BMW řady 3 vs. Mercedes-Benz C-Class: Complete comparison 2026

BMW 3 Series, also known by its international designation BMW 3 Series or popularly abbreviated as the "Three", has long been the benchmark for sporty premium mid-size cars thanks to its uncompromising emphasis on precise handling and driving dynamics. Its arch-rival, Mercedes-Benz C-Class, sold on the local market mainly under the name Mercedes-Benz C-Class or simply the "C", on the contrary, traditionally brings an aura of unrivaled elegance, innovative technologies, and top-tier ride comfort to this segment. Let's now take a detailed look at which of these two long-standing German rivals represents a better choice on the young used car market for your daily commutes and driving experiences.

In the premium mid-size segment, exterior dimensions play a key role as they must balance a representative appearance, sufficient interior space, and everyday urban usability. If we focus on the models that currently dominate the market for nearly new used cars around four years old (specifically the BMW G20/G21 and Mercedes-Benz W206/S206 generations), we find that both rivals are very close in their proportions, yet they maintain their specific character and focus.

The Mercedes-Benz C-Class in its current generation is slightly longer and bets on a more elongated, majestic silhouette. With a length of 4751 mm, it exceeds the BMW 3 Series (4709–4713 mm) by about 40 mm. This increase is also positively reflected in the wheelbase, which for the Mercedes is 2865 mm—14 mm more than its Munich competitor. For passengers, this means slightly more longitudinal space in the cabin and, theoretically, a smoother, more stable ride on long highway journeys.

Conversely, the BMW 3 Series stands out with its slightly wider stance. With a width of 1827 mm, it is 7 mm wider than the Mercedes-Benz (1820 mm). Although this seems like a negligible detail, the wider track and slightly shorter wheelbase contribute to the typically sporty and more planted stance on the road, which is especially appreciated during dynamic cornering. In terms of height, the base models are very similar; however, greater differences appear in the estate body variants (Touring for BMW, Estate for Mercedes). Particularly if you opt for the Mercedes All-Terrain version with its plastic cladding, the vehicle's height increases up to 1494 mm.

From a practical standpoint, the difference in length between the two cars is almost unnoticeable when parking in tight city garages; however, the slightly more compact build of the BMW may give drivers a bit more confidence when maneuvering. Overall, the Mercedes-Benz C-Class scores with its elegance and effort to maximize comfortable longitudinal space, while the wider profile of the BMW 3 Series clearly signals its driver-oriented nature and traditional focus on agility.

Comparison of exterior dimensions (models from 2019 onwards)

Luggage space is a key parameter for many used car buyers, especially if they are choosing a premium mid-size model for daily family use or long business trips. When comparing the approximately four-year-old generations that currently dominate the used car market – namely the BMW 3 Series (G20/G21 generation) and the Mercedes-Benz C-Class (W206/S206 generation) – it is clear that both brands have tried to maximize the usability of every available centimeter. While the differences in size may not seem vast on paper, in practice they can mean that missing space for a few extra suitcases or easier loading of bulky sports equipment.

For classic three-box body styles, the BMW 3 Series offers a slightly more generous 480 liters of base volume, while the Mercedes-Benz C-Class sedan lags slightly behind with 455 liters. However, in the used car market, estate variants are disproportionately more in demand for family purposes. Here, the BMW 3 Series Touring provides 500 liters of storage space, which can be increased to a great 1,510 liters after easily folding the rear seats. The Mercedes-Benz C-Class estate (T-Modell) follows closely with a base volume of 490 liters and an identical maximum space of 1,510 liters. The values for both cars are perfectly sufficient for weekend shopping or a longer holiday. However, those interested in modern plug-in hybrid versions must be careful. The placement of large traction batteries takes its toll – in the hybrid BMW, the volume drops to 375 liters (410 liters for the estate), while in the rival Mercedes C-Class, the value shrinks to just 315 liters for the sedan and 360 liters for the estate.

Overall, the BMW 3 Series comes out slightly ahead in this luggage duel. The Bavarian model provides a slightly larger base volume for both body styles and also shows better space packaging for plug-in hybrids, where it doesn't lose as much capacity as its Stuttgart challenger. While Mercedes-Benz lags slightly in the base, it manages to keep pace with the more practical estate body style after folding the seats, which erases any minor handicap in the eyes of many buyers.

The ability to tow a trailer is a key parameter for many owners of premium mid-size cars, whether for hitching up a caravan or simply for a significant boost in everyday practicality. When comparing used cars approximately four years old, we find that both brands offer very solid values, albeit with noticeable differences in consistency across the range.

Mercedes-Benz C-Class (especially models from the end of the W205 generation and the newer W206) confidently maintains a uniform maximum braked trailer weight of 1800 kg for standard internal combustion engines such as the C 200 and C 200 d. In contrast, the BMW 3 Series (G20/G21 generation) shows a slightly wider range. While standard 320i and 320d models usually start at 1500 to 1600 kg, they can also reach a maximum of 1800 kg depending on the specific equipment and specification.

Buyers considering plug-in hybrids should pay close attention. While conventional engines push the limits high, the electrified BMW 320e has a permanently reduced capacity that does not exceed 1500 kg due to the additional weight of the batteries. In real-world use, these parameters mean that even with a smaller trailer attached, you gain the necessary space for several extra suitcases. The highest braked trailer values are thus fully sufficient for a weekend shopping trip or a longer holiday in a heavier family caravan.

Overall, both cars are excellently dimensioned for towing. Mercedes customers can rely on a higher level of general certainty regarding maximum load, while with BMW, it is necessary to choose more purposefully and verify capacities according to the specific specification in the vehicle registration document. (Note: Data regarding unbraked trailer weights for these specifications are not listed in our database and are therefore marked as "No data" in the table. However, the common standard for this class of vehicles is usually 740–750 kg).

BMW 3 Series (G20/G21 generation) and Mercedes-Benz C-Class (W206/S206 generation) offer customers on the used car market – typically for roughly four-year-old vehicles – a very advanced, yet philosophically differently conceived range of engines. While Mercedes-Benz made a radical cut with its latest W206 generation and limited all its engines exclusively to four-cylinders with 48V mild-hybrid technology, BMW remained faithful to a more diverse range of displacements for the 3 Series and continues to offer its iconic straight-six 3.0-litre engines. From the perspective of everyday life, this means that with Mercedes you always get a technologically unified architecture designed for the smoothest possible response and efficiency, while with BMW you still have the option to go for a classic large-displacement experience. However, both brands excel in offering 2.0-litre diesel four-cylinders for high mileage and score points with advanced plug-in hybrids, whose real-world electric range has moved forward significantly compared to previous generations.

Engine Range: BMW 3 Series (G20/G21)

Under the hood of the Bavarian representative from 2019 to 2022, you will find a wide spectrum of power units, dominated in the 2.0-litre four-cylinder category by the petrol 320i with 135 kW and the legendarily efficient diesel 320d tuned to 140 kW. Most of these cars rely on the perfectly tuned eight-speed Steptronic automatic transmission. As historical production data confirms, manual transmissions for this generation completely disappeared from the range over the years, so coming across them in a four-year-old used car is an absolute rarity. A huge asset and attraction of BMW, however, is the retention of the sonorous six-cylinder 3.0-litre engines in top specifications, such as the motorway mileage eater 330d or the sportily-tuned M340i xDrive. In terms of electrification, BMW offers highly sought-after plug-in hybrids with a two-litre base – the 320e and 330e models.

Engine Range: Mercedes-Benz C-Class (W206)

The W206 generation, present on the market since 2021, brought literally a small revolution under the hood. All power units from this model year onwards are exclusively modular four-cylinders (which also applies to the sporty AMG versions, which have completely lost their classic V8 engines). With roughly four-year-old used cars, you are therefore guaranteed to get an engine with the most modern 48V mild-hybrid architecture, where an integrated starter-generator (ISG) compensates for turbocharger lag and adds a short-term power "boost" of 15 kW (20 hp) to the vehicle. Lightning-fast shifting is then handled exclusively by the nine-speed 9G-TRONIC automatic. The entry-level petrol variants C 180 and C 200 use a smaller 1.5-litre displacement, while the more powerful C 300 relies on a classic 2.0-litre four-cylinder. The diesel portfolio (represented by the C 200 d and C 220 d models) bets on a redesigned two-litre, which dominates with phenomenal real-world fuel consumption. A chapter of its own is the plug-in hybrid variant C 300 e, which at the time of its launch shocked with a massive 25.4 kWh battery ensuring a real-world emission-free range bordering on 100 kilometres.

Engine Comparison from a Driver's Perspective

If you are comparing used cars of these two models, the engine should be chosen exactly according to what you will primarily use the vehicle for:

• For motorway drivers and fuel economy hunters: An exceptionally good choice is the diesel BMW 320d with its brilliant automatic or the efficient Mercedes-Benz C 220 d. Mercedes achieves slightly smoother operation in city traffic jams thanks to its powerful ISG electric motor connected directly to the transmission, while BMW is the choice for those who appreciate a slightly firmer and sportier throttle response.
• For users looking for electrification: The Mercedes C 300 e plug-in hybrid surpasses the rival BMW 330e with its mammoth battery. This provides the car with almost double the pure electric range compared to the BMW model, which represents a huge advantage for people with the possibility of home charging.
• For purists and those interested in dynamics: If you swear by the characteristic burbling sound and linear power of three-litre six-cylinders, then BMW is the clear winner in this comparison (the 330d or M340i versions). In the C-Class from the W206 generation onwards, you will no longer find a multi-cylinder engine.

Choosing the right engine is absolutely crucial for long-term satisfaction with the car. Our recommendations are based on real-world mechanical experience, proven reliability, actual fuel consumption, and overall feedback from owners. Historically, both brands on the European market rely primarily on reliable two-liter diesels, which in approximately four-year-old nearly new used cars have evolved into highly refined and extremely efficient mild-hybrid units. As production history data records confirm, problematic engines of older generations have long since ceased production, and in the market for four-year-old vehicles (such as the BMW G20 generation and Mercedes-Benz W206), you are safely choosing from technically exceptionally refined and durable versions. While the Bavarian engine delights with its sportier sharpness, the Stuttgart competitor bets on absolute silence and velvety operation.

For the BMW 3 Series, we recommend: 320d (140 kW)

This two-liter diesel (code B47), widely represented in approximately four-year-old G20 generation cars, represents the absolute gold standard for the "Three." Why it's the best choice: It offers an excellent compromise between driving agility and everyday practicality. The dreaded problems with stretched timing chains from the older N47 engine are reliably solved in the updated B47 engine, making it one of the most durable diesels on the market. Technical advantages: It features a strong torque of 400 Nm from very low revs and exemplary real-world fuel consumption between 5.0 and 5.5 liters per 100 km. In perfect harmony with the precise eight-speed ZF gearbox, it practically has no dynamic competition. Risks and what to watch out for: A typical weakness in modern diesel BMWs is the exhaust gas recirculation (EGR) cooler, which poses a risk of a hidden coolant leak. How to tell: During the car inspection, open the hood and check the coolant level in the expansion tank – a drop below the minimum is a major warning sign. At the same time, verify with the dealer using the VIN whether the car has already undergone a recall repair. Another risk is a clogged DPF filter due to exclusively city driving. How to tell: A faulty or clogged filter often manifests as rougher engine operation and constantly increased idle speeds, as the car tries in vain to start regeneration. Who it's ideal for: The 320d engine is made for drivers swallowing long highway kilometers who are looking for economical operation but at the same time do not want to lose the typical Bavarian driving pleasure.

For the Mercedes-Benz C-Class, we recommend: C 200 d (120 kW)

For modern nearly new used cars of the W206 generation (or late W205 models), the two-liter diesel of the OM654M generation is an ideal and highly rational companion. Why it's the best choice: Although it is a more moderate power tuning of this unit, the 120 kW output is absolutely confident for safe overtaking and long-distance travel. Compared to more powerful versions, it represents a more affordable yet mechanically equally bulletproof variant that perfectly maintains the brand's legendary smoothness. Technical advantages: The engine fully benefits from a sophisticated mild-hybrid system (EQ Boost). The auxiliary electric motor completely masks turbo lag and ensures perfectly quiet engine restarts via the start-stop system. Consumption commonly falls well below the 5-liter mark, and the reliable nine-speed 9G-TRONIC automatic transmission manages to keep highway revs at an absolute minimum. Risks and what to watch out for: The complex emission system combining an SCR catalyst (AdBlue) and DPF is very sensitive to short-distance driving, which leads to urea crystallization and subsequent damage to valuable NOx sensors. How to tell: During the test drive, carefully go through the on-board computer menu and watch for AdBlue faults or a warning yellow engine light. Also focus on the smooth operation of the transmission and request a test drive with a completely cold car. How to tell: Shifting between 2nd and 3rd gear must occur almost imperceptibly; a distinct jerk may indicate the need for a transmission flush or software adaptation. Who it's ideal for: This powertrain will primarily delight calmer and comfort-oriented drivers for whom absolute driving serenity, excellent acoustic insulation, and unrivaled operating efficiency on long routes are priorities.

Paper fuel consumption figures provided by manufacturers according to the WLTP measurement standard often differ from the reality of everyday driving. While both premium brands promise miraculously low figures for their current models in the laboratory, the reality on the road reveals a much more realistic picture. For an accurate and objective comparison of used cars around four years old (belonging to the BMW G20 and Mercedes-Benz W206 generations), we have used real user data from crowdsourcing platforms where thousands of drivers record their actual refueling.

Data source: Spritmonitor.de

Looking at the real data, it is clear that diesel engines still reign supreme for motorway travel. The Mercedes-Benz C 200 d proves to be the absolute champion in efficiency, commonly dipping below five and a half liters in practice, despite its relatively high kerb weight. Although the BMW 320d is two-tenths of a liter thirstier, it should be noted that it offers significantly higher rated power and more spirited dynamics. A rather interesting trend emerges with the petrol variants – even advanced technologies and mild-hybrid systems cannot always compensate for the strain of city traffic as the brochures claim. In the real world, the entry-level four-cylinder two-liter engines consume over seven liters per hundred kilometers, with the Munich representative being slightly more economical. It remains a surprise that the otherwise highly sophisticated EQ Boost electrification in the Mercedes does not bring more tangible fuel savings in real life compared to the more traditional tuning of the BMW powertrain.

What does this mean for the typical buyer in the used car market? If you are a motorway traveler or a manager who covers tens of thousands of kilometers a year, both diesel engines represent an absolutely phenomenal choice with a huge range on a single tank and minimal fuel costs. The Mercedes will please calmer drivers focused on absolute efficiency, while with the BMW, you get a slight performance advantage with only a negligible increase in consumption. However, for drivers who spend most of their time in city traffic jams or drive shorter distances, the petrol versions make much more sense. While you have to expect a higher bill at the petrol station with these, in the long run, you will likely avoid expensive service interventions for complex diesel emission systems, which simply do not benefit from constant cold starts.

The overall assessment clearly shows that fuel consumption itself is unlikely to be the main deciding factor that tips the scales in favor of one car or the other. Both premium carmakers offer such advanced and optimized engines in their four-year-old models that their real-world operating efficiency is almost identical. Your final choice should therefore be based more on which overall character of the car is closer to you – whether you prefer the stiffer and sportier performance typical of BMW, or rather the soothing, insulated, and comfortable ride with the Stuttgart star.

Price range of used cars (models around 4 years old)

When choosing a roughly four-year-old used car (production years 2021–2022), we are looking at a very attractive market for both German automakers. For these model years, BMW offers the proven and widely available G20 generation (or G21 Touring) before the facelift. In contrast, with Mercedes-Benz, you will encounter a major generational shift in the same period – the outgoing W205 series and the incoming, technology-packed W206 generation. This fact significantly impacts the price range on the used car market.

BMW 3 Series (Generation G20/G21)

The BMW 3 Series is exceptionally popular on the used car market, and thanks to a wider selection and the fact that this generation has been on sale since 2019, there is a very pleasant price drop for four-year-old cars.

• Affordable entry (318i, 320d with higher mileage): 2021 and 2022 models with mileage approaching 150,000 km can be found on the market starting from approximately €18,000 to €25,000. This is the most affordable ticket to the premium segment with rear-wheel drive.
• The golden middle ground (320d xDrive, 330i): Well-equipped models in sedan or the more popular Touring (estate) versions with reasonable mileage around 60,000 to 100,000 km are most often purchased in the range of €27,000 to €37,000. This is where BMW excels with an unbeatable price-to-performance and equipment ratio.
• Top engines (M340i, M340d): Sporty and highly desirable six-cylinder models hold their value significantly better. Their price tags usually start just above the €45,000 mark.

Mercedes-Benz C-Class (Generation W205/W206)

The market for roughly four-year-old C-Class models is more specific. If you are looking for a cheaper option, the market offers the last units of the outgoing generation, but Mercedes will charge generously for modern technology.

• End of the W205 generation (until 2021): Used cars of the previous generation with popular diesel engines and higher mileage range in price from around €25,000 to €29,000.
• Arrival of the W206 generation (C 200, C 220 d): The W206 generation, which arrived on the market at the turn of 2021/2022, brought an interior in the style of the flagship S-Class and advanced mild-hybrid powertrains. These four-year-old cars hold their price significantly higher, and you should prepare amounts mostly from €31,000 to €47,000.
• High-performance AMG versions (C 43, C 63): Luxury and enormous performance traditionally lose value the slowest. Well-maintained performance variants of the W205 generation commonly range between €62,000 to €103,000, while prices for the newer W206 are even markedly higher.

Residual value assessment

From the perspective of a used car hunter, a four-year-old BMW 3 Series makes fantastic sense. The optimal price drop makes it a more affordable choice for drivers who want excellent driving characteristics without the need for a huge investment.

The Mercedes-Benz C-Class in the 2021–2022 model years is price-burdened by the generational change. If you go for the newer W206 model, the purchase price will be significantly higher than for a comparable BMW, but in return, you get a car with a more modern technological arsenal that will age visually much more slowly.

Context of the Five-Star Rating

Both cars, the BMW 3 Series and the Mercedes-Benz C-Class, can boast the best possible result – a maximum five-star rating in independent crash tests by Euro NCAP. However, it is extremely important to put these results into the correct context and take the year of testing into account. The Euro NCAP methodology is constantly evolving and becomes stricter practically every year. For this reason, percentage scores from different years are not directly comparable. Newer car models must face much more demanding simulations, including more precise cyclist detection, more complex intersection scenarios, or the evaluation of advanced passive safety features.

Safety in the BMW 3 Series (G20)

The current generation of the BMW 3 Series (G20) underwent a series of rigorous barrier tests in 2019. The car truly shone in the area of adult occupant protection, where it achieved an impressive 97%. At the time of testing, it was the best result ever in the large family car segment. Child protection was rated at a very solid 87%, and the sedan scored the same in the protection of vulnerable road users, benefiting mainly from a sophisticated active hood system that protects pedestrians. In the safety assist category, which was not as strictly assessed back then, the Munich model earned a reliable rating of 76%.

Safety in the Mercedes-Benz C-Class (W206)

The latest generation of the C-Class (W206) faced crash tests in 2022. It had to deal with significantly stricter requirements across all categories. Even under these tougher conditions, it achieved excellent adult protection (93%) and child protection (89%). Mercedes scored highly, among other things, by deploying an innovative center airbag that effectively prevents the heads of front-seat passengers from colliding during a side impact. The car demonstrated a significant technological leap in the safety assist category, where it recorded an excellent 82% even under the stricter standards. The testing committee praised the reliable autonomous braking system, which reacts flawlessly to cyclists and vehicles approaching from the side at confusing intersections.

Overall Evaluation of Safety Equipment

Although the BMW 3 Series still impresses today with its unrivaled passive rigidity and occupant protection in frontal impacts, the 2022 Mercedes-Benz C-Class fits current safety trends slightly better thanks to its newer pedigree. This mainly concerns the higher maturity of active features and assistants for preventing crisis situations, making the Stuttgart model a slightly more comprehensive package in terms of everyday modern protection.

Beyond standard equipment, both models offer much more than just basic functions for daily commutes, with each taking its own approach to added value.

BMW 3 Series: Driver Focus and Smart Practicality

• Infotainment and Ergonomics: The Munich-based automaker sticks to the proven iDrive concept with a physical rotary controller on the center console. This solution remains unsurpassed in terms of driving ergonomics, allowing for intuitive control without taking your eyes off the road. There is also the option to unlock and start the car using a digital key on a smartphone.
• Smart Assistance Systems: A truly unique feature is the Reversing Assistant. The system remembers the last 50 meters driven forward (at speeds up to 36 km/h) and can autonomously reverse out along the exact same trajectory, which is invaluable in narrow streets or confusing garage entrances.
• Lighting Technology: In better-equipped used cars, you may come across optional laser headlights (BMW Laserlight). These excel with an extreme high-beam range that safely illuminates even the darkest country roads.
• Iconic Practicality (Touring version): The estate traditionally offers the legendary independently opening rear window, ideal for quickly tossing in groceries. In higher trim levels, the luggage compartment also features smart retractable anti-slip rails that rise slightly after the trunk is closed to prevent luggage from moving.
• Sporting Spirit: Models equipped with the popular M Sport package bring not only a more aggressive look but also an adaptive M suspension and variable sport steering. These features can transform a comfortable highway cruiser into a precise tool for driving fun at the touch of a button.

Mercedes-Benz C-Class: A Miniature S-Class and Technological Dominance

• Connectivity and User Interface: The interior is dominated by the MBUX system with a massive vertically oriented touchscreen that flows seamlessly into the center console. It includes one of the best voice assistants on the market, activated by the command "Hey Mercedes".
• Augmented Reality: Higher trim levels feature navigation with augmented reality (AR). The system displays a live feed from the front camera on the central display and virtually renders directional arrows, street labels, and navigation instructions onto it in real-time.
• Chassis and Handling: A major technological innovation is rear-axle steering (up to 2.5 degrees). In the city, it reduces the turning circle by nearly half a meter for easier parking, while at higher speeds, it stabilizes the car during quick direction changes.
• Digital Light: Mercedes' top-tier headlights don't just provide perfect road illumination without dazzling others; they also function as projectors. They can project warning symbols onto the road (e.g., roadwork alerts) or guidance lines for narrow lanes.
• Powertrain and Electrification: The W206 generation (from 2021) is exclusively electrified. Even the base mild-hybrid engines ensure perfectly smooth and quiet starts thanks to the integrated starter-generator (ISG). The highlights are the plug-in hybrid versions, which boast a massive battery and a real-world pure electric range exceeding 100 km, fundamentally changing the economics of daily commuting.
• Onboard Atmosphere: The C-Class openly adopts the design and atmosphere of the flagship S-Class. The sense of comfort is enhanced by top-tier ambient lighting with 64 adjustable colors, which also illuminates the air vents, bringing a touch of true luxury to the mid-size segment.

BMW 3 Series is a perfect choice for enthusiastic drivers who demand not only daily practicality from their car but also top-tier handling and driving experiences. Thanks to great ergonomics and the availability of powerful six-cylinder engines, it represents an ideal sporty executive car.

Mercedes-Benz C-Class will primarily appeal to customers who prioritize maximum comfort, a luxurious appearance, and the latest technology. It is a perfect highway cruiser that can isolate the occupants from the outside world with its quiet and smooth ride.

Based on our own breakdown statistics, long-term owner experiences, and the reports provided by every one of our physical used car inspections, we have compiled an overview of the most common problems. For roughly four-year-old used cars of these two premium rivals, you should watch out for the following weak points.

BMW 3 Series (G20 generation)
With the G20 generation, the Bavarian automaker has returned to the top in terms of reliability. Although the mechanical foundation is considered very durable, the early model years did not escape minor ailments.

• Coolant leaks: Both gasoline (B48 and B58) and diesel engines (B47) are overall above-average in reliability. However, with increasing mileage, coolant leaks occasionally appear, most often due to a cracking seal around the oil filter housing or at the turbocharger hoses.
• Electronics and hybrid system: Owners of the popular plug-in hybrids (330e) quite often report charging issues or confusing error messages, which paradoxically often originate from a weak conventional 12V battery. System errors are mostly resolved by software updates.
• Assistance systems: A specific defect regarding the lane-keeping assistant is known. If it stops working (error 800A07 is stored in the memory), the culprit is usually a faulty vibration motor directly in the steering wheel.
• Interior: Many owners complain about occasional creaking of the sunroof on uneven surfaces in an otherwise excellently crafted interior. It is recommended to regularly clean the window mechanism and lubricate it with a dry lubricant.

Mercedes-Benz C-Class (W206 generation)
The latest C-Class is literally a rolling laboratory of modern technology. Unfortunately, this takes its toll on the early model years in the form of teething troubles, mainly associated with complex electronics.

• MBUX Infotainment: The onboard system is among the most frequent targets of complaints. Freezing, spontaneous restarts, black screens, or dropped connections when using Apple CarPlay and Android Auto are quite common in 2021 and 2022 models and usually require a service visit to install new software.
• Mild-hybrid system (EQ Boost): A failure of the 48V network and the integrated starter-generator (ISG) can cause major problems. The defect often manifests as a non-functional start-stop system, rapid battery discharge, and in extreme cases, an error message on the instrument cluster "Engine cannot be started," which completely immobilizes the vehicle.
• Oil consumption in gasoline engines: In M254 four-cylinder gasoline units, owners report increased engine oil consumption. This can be caused, among other things, by a clogged positive crankcase ventilation (PCV) system. Owners are therefore recommended to use the electronic oil dipstick more frequently.
• Interior craftsmanship: In direct comparison with its Bavarian competitor, some owners complain about the cheaper feel of some materials, and occasional creaking and rattling of interior plastics. There are also isolated false reports from tire pressure sensors (TPMS) or airbag warning lights.

When buying a used car, a thorough inspection is key, and especially with premium brands, neglecting any detail can become unpleasantly expensive. A comprehensive car audit can give you peace of mind before buying, but you should also focus on your own impressions during the test drive. Here are several specific points to focus on for these two popular models.

When choosing a BMW 3 Series:

• iDrive infotainment functionality and smoothness: Thoroughly click through all system functions. Earlier versions of iDrive software can occasionally freeze or have stability issues with wireless Apple CarPlay and Android Auto. Check the settings to see if the latest OTA (Over-The-Air) software updates have been performed.
• Steering play and chassis: During the test drive, intentionally drive over several bumps or potholes and listen for any dull knocking from the front axle. Models with adaptive M suspension may show earlier wear on tie rod ends and shock absorbers. Steering should be perfectly precise at all times and without play in the center position.
• Brake system condition (especially M Sport version): Visually check the lip depth on the discs and, when braking slowly (e.g., before an intersection), roll down the window and listen. Sport brakes on BMWs wear out relatively quickly and often squeal. Rapid wear means an early and often costly investment in new discs and pads.
• xDrive transfer case jerking: On all-wheel-drive versions, acceleration should be perfectly smooth under all circumstances. If you feel slight jerking or vibrations during acceleration, it could be a worn transfer case. This fault often occurs if the previous owner drove on tires with incorrect or differing circumferences.
• Plug-in hybrid battery (330e): On electrified versions, focus on the smoothness of switching between electric and combustion modes – the transition should be almost imperceptible. Also, have the current high-voltage battery capacity (State of Health) checked via diagnostics to be sure about the real electric-only range.

When choosing a Mercedes-Benz C-Class:

• 48V mild-hybrid system behavior (EQ Boost): Almost all engines of the latest generation rely on mild-hybrid technology. During a cold start or when the start-stop system wakes up at an intersection, the engine must start smoothly and immediately. Hesitation, delays, or warning lights can indicate an expensive problem in the 48V network.
• MBUX interface stability: The huge central display on the center console controls the vast majority of the car's functions, including the air conditioning. Test how quickly the touchscreen and voice control respond. Find out if the system restarts for no reason during the drive, which was a common ailment in the early years of the W206 generation and usually requires a software intervention.
• 9G-Tronic nine-speed transmission smoothness: During the test drive, let the car slow down slowly without throttle and observe the automatic's behavior when downshifting (especially from 3rd to 2nd and 2nd to 1st gear). Any hard jolts or jerking, especially when cold, may mean the transmission software needs calibration or an immediate oil change is required.
• Interior build quality and creaks: Although Mercedes-Benz excels in luxury design, the build quality of some plastics can loosen over time. Try listening for creaks from the center console while driving on cobblestones. You can also try pressing lightly on the edges of the plastics around the central display – the car should not make cheap plastic sounds.
• Brake blending on plug-in hybrids (C 300 e / C 300 de): These models offer excellent pure electric range; however, the transition between regenerative (electric) braking and classic mechanical brakes can sometimes be inconsistent. Try both sharp and very gentle braking to see if the pedal feels "wooden" and if its resistance is predictable. As with the BMW, insist on checking the current degradation of the battery module.

Sources: ADAC, auto.cz, aktualne.cz, automagazin.cz, motorvize.cz, automotorista.cz

This article was prepared using artificial intelligence tools. The section guarantor is Petr Dušek.