Audi A4 vs. BMW řady 3: Complete comparison 2026

The Audi A4, also known on the market by its internal generation designation B9 and in the practical estate body style as the Avant, represents the benchmark of precise German engineering with a focus on timeless design and top-tier interior craftsmanship. In contrast, the BMW 3 Series, popularly nicknamed the "three" and hidden under the factory codes G20 for the sedan or G21 for the Touring estate, has long defined the absolute standards of sporty driving characteristics and driving pleasure in the premium mid-size class. Now we will take a detailed look at how these long-time rivals stand in a direct comparison and which of them represents a more tempting choice when buying on the market for nearly-new used cars.

When comparing external dimensions on the used car market – focusing on models roughly four years old, namely the currently widely represented Audi A4 (B9) and BMW 3 Series (G20/G21) generations – we encounter very interesting conceptual differences. In its facelifted versions, with a length of 4,762 mm, the Audi A4 is 49 mm longer than the rival BMW 3 Series, which measures 4,713 mm. The Ingolstadt representative is also 20 mm wider (1,847 mm compared to 1,827 mm for the BMW). In practice, this means the Audi feels slightly more robust and expansive on the road. Conversely, the BMW's advantage is slightly easier maneuverability in cramped urban spaces, while the Audi's wider and longer body may require a bit more caution when parking in tight garages. Differences in overall proportions thus highlight the choice between the Audi's elegant robustness and the BMW's more compactly tailored dynamics.

However, a much more significant difference can be found in the wheelbase, which is absolutely key for both interior space and overall driving characteristics. The BMW 3 Series boasts a generous wheelbase of 2,851 mm, which is a full 31 mm more than what the Audi A4 offers (2,820 mm). This technical detail clearly stems from the traditional Munich architecture, which favors rear-wheel drive and allows the front axle to be pushed as far forward as possible. The advantage of the longer wheelbase in the BMW is reflected not only in higher directional stability on the highway but also in shorter body overhangs. Audi, on the other hand, builds on a concept with a longitudinally mounted engine positioned further over the front axle, which logically extends the front overhang. You will thus be choosing between the BMW's more athletic and balanced stance on one hand and the confidence stemming from the Audi's robustly tailored overhangs on the other.

The height of both vehicles is very similar, although minor differences appear here as well. Depending on the version and body style, the BMW 3 Series rises to values between 1,435 and 1,445 mm, while the Audi A4 Sedan sits slightly lower to the ground with a height of around 1,428 mm. In the popular estate body variants (Avant for Audi and Touring for BMW), both cars meet in an almost identical range above 1,434 mm. The overall design direction shows that Audi engineers focused on visually lowering and widening the body for this model. As a result, the Audi makes sense primarily for those who prefer a visually wide car with a strong presence, while for the BMW, the primary factor is that fantastic wheelbase dictating unrivaled sporty proportions.

External Dimensions Comparison Table

Here is an overview of key values for models roughly four years old (B9 generation for Audi and G20/G21 for BMW). Minor variations based on equipment, potential packages, or slight facelifts during the period are taken into account.

Luggage space is often a deciding factor for both families and managers who spend a lot of time on the road. Although both the Audi A4 and the BMW 3 Series belong to the premium mid-size class, where driving dynamics and comfort usually take precedence, both models can offer very solid practicality. When choosing a roughly four-year-old used car, you will most often focus on the current generations – Audi A4 (B9) and BMW 3 Series (G20/G21). While the differences in boot volumes are not vast at first glance, they have their indisputable significance for a detailed comparison of family usability.

Looking at the classic three-box body styles, the BMW 3 Series Sedan offers a base volume of 480 liters, slightly surpassing the Audi A4 Sedan with its 460 liters. In practice, this difference provides space for a few extra suitcases, making the Munich model feel somewhat more usable overall. However, be careful when choosing plug-in hybrid versions, which you can find in abundance on the used car market. The battery placement in the BMW 320e model reduces the sedan's boot capacity to just 375 liters, which may already necessitate compromises when packing for a family.

Much more sought-after variants for family use on our market are the practical estate versions, where the battle is even closer. The BMW 3 Series Touring (Estate) provides a basic luggage compartment of 500 liters, while the Audi A4 Avant (Estate) follows closely with 495 liters. After folding down the rear seats, the BMW offers a maximum transport capacity of 1510 liters, while the Audi stays close behind with 1495 liters. In any case, both of these values are perfectly sufficient for a weekend shopping trip or a longer holiday. Alternative powertrains must be considered again – for the BMW Touring, the volume drops to 410 liters in the plug-in hybrid version (1420 liters when folded), while for the Audi in the g-tron (CNG) gas version, you will measure 415 liters at base and 1415 liters with the seats down.

In terms of absolute numbers, BMW emerges as the slight favorite from this duel, although for the immensely popular estate versions, we are talking about a difference of only five liters in base volume. Both representatives will serve you without hesitation for everyday family travel, so the main decision will lie more in the choice of engine and accepting the smaller boot in hybrid variants.

Towing Capacity and Trailer Weight

When choosing a premium mid-size car intended for an active lifestyle, trailer weight plays a key role. For many buyers, towing capacity is the deciding factor, whether it's for hauling construction materials on the weekend or summer travel with a caravan. In approximately four-year-old used cars – namely the Audi A4 (B9 generation) and BMW 3 Series (G20/G21 generation) – we find interesting differences in this regard that can tip the scales one way or the other.

Both the base and maximum braked trailer weight values differ between the two rivals. The BMW 3 Series offers a very confident baseline – for most common engines, such as the 320i or 320d models, the standard braked trailer weight is a generous 1,600 to 1,800 kg. In contrast, the Audi A4 starts with a towing capacity between 1,400 and 1,500 kg for its base petrol (e.g., 35 TFSI) or weaker diesel versions (30 TDI). However, if you opt for more powerful engines, such as the six-cylinder Audi A4 50 TDI, the maximum braked trailer weight climbs up to 1,900 kg. Both manufacturers have set the maximum unbraked trailer weight for these model series at the European legislative limit of 750 kg.

When choosing, it is also necessary to pay attention to electrified versions, where limitations often occur. For example, the plug-in hybrid BMW 320e has its maximum braked trailer capacity reduced to a fixed 1,500 kg. Similar values (1,400–1,500 kg) for Audi's base and economical engines mean that while the car can easily handle a smaller trailer sufficient for weekend shopping or hauling garden waste, it may represent a compromise for a heavy family caravan. Conversely, more powerful versions from both brands provide plenty of reserve for towing a large caravan or worry-free boat transport.

Conclusion: If towing heavy trailers is a daily priority for you, the BMW 3 Series offers the assurance of more stable and higher values (1,600–1,800 kg) starting from mid-range trim levels and common four-cylinder engines. The Audi A4 only reaches similar or higher figures with more powerful two-liter engines (40 TDI) or top-of-the-line six-cylinders (50 TDI with an excellent 1,900 kg), which simply requires a slightly more careful selection of a specific unit on the used car market.

Different Worlds of Longitudinal Engines: Ingolstadt vs. Munich

Both of these premium carmakers approach their powertrain offerings with a different philosophy, although they share the advantage of a premium architecture with longitudinally mounted engines. While the Audi A4 (B9 generation) benefits from the advanced MLB Evo platform and offers a superbly sound-insulated range of mild-hybrid petrol and diesel engines – including the legendary 3.0 TDI V6s – the BMW 3 Series (G20/G21 generation) relies on the more dynamic Munich school. The CLAR architecture gives the Bimmer ideal weight distribution, primary rear-wheel drive, and, unlike the Audi, a strong lineup of plug-in hybrids (e.g., 320e and 330e versions). For those interested in an attractive four-year-old used car (around the 2022 model year), this means that at Audi, they will find a dominance of highway-tuned diesels and S tronic dual-clutch transmissions, while BMW will satisfy drivers seeking a sportier character with the silky eight-speed Steptronic torque-converter automatic. Both brands rely primarily on two-liter four-cylinder units as standard, but connoisseurs will also find what they're looking for thanks to the authoritative top-tier six-cylinders.

Audi A4: Simplified Displacements and a Bet on Highway Diesels

The engine range for the Audi A4 after the significant facelift (often referred to as B9.5, cars from roughly late 2019 to 2024) underwent a renaming and simplification of displacements. In the data from available production years, you can notice that the previous base engine, the 1.4 TFSI, is now completely missing from the newer models' lineup – it gradually disappeared from the price lists. Instead, the current petrol base for younger used cars is an efficient but detuned two-liter four-cylinder bearing the 35 TFSI designation. The centerpiece of used car sales for roughly four-year-old cars is, in any case, the economical 2.0 TDI diesel (from 30 TDI versions to the popular 40 TDI), which is considered an unsurpassed benchmark for long-distance highway travelers. The vast majority of these engines are paired with a seven-speed S tronic dual-clutch automatic transmission. If you're aiming for the absolute top of the standard range, the majestic 3.0 V6 diesel awaits you in the 45 TDI and 50 TDI variants. Unlike the weaker versions, this one works exclusively with an eight-speed Tiptronic torque-converter automatic and permanent quattro all-wheel drive.

BMW 3 Series: Traditional Driving Pleasure and the Rise of Electrification

The Bavarian competitor, the BMW 3 Series (current G20/G21 generation), brings slightly different dynamics and broader electrification options to the used car market. While for young, roughly four-year-old models, the market mainstream consists of similarly conceived petrol and diesel two-liters (very often available 320i and 320d variants), BMW stubbornly cherishes its tradition and has managed to keep petrol straight-sixes in the lineup – namely the M340i with an uncompromising 275 kW of power. A major trump card for those interested in low-emission mobility is BMW's strong support for plug-in hybrid systems represented by the 320e and 330e models, which you won't find at all in the competing Audi of the generations examined. A significant change in the market for younger used BMWs affected shifting – while it was previously possible to choose, classic manual transmissions have practically disappeared from the range (appearing only in the base 318d from the first years of production), and the role has been fully taken over by the phenomenal and reliable eight-speed Steptronic torque-converter automatic from ZF. This can be configured with either classic rear-wheel drive or the xDrive system.

Which Range to Choose?

• Highway drivers and long-distance travelers: Both cars excel, however, the Audi A4 with its efficient 35 TDI and 40 TDI engines represents the absolute peak in long-term fuel economy, better four-cylinder sound insulation, and highway serenity.
• Drivers oriented towards sportier performance: If you appreciate an immediate throttle response and the perfect interplay of the drivetrain with a lightning-fast transmission, BMW's two-liter units (320i, 330i, and the proven 320d diesel) will put a noticeably wider smile on your face on your favorite backroad.
• Those interested in alternative powertrains and multi-cylinder icons: Those interested in quiet daily city driving with charging have nothing to think about – plug-in hybrids are BMW's domain. Furthermore, both camps will reliably satisfy even the most demanding buyers with their charismatic three-liters – the 50 TDI diesel in the Audi and the M340i petrol in the BMW.

Choosing the right engine is absolutely crucial for long-term satisfaction with a car. Our recommendations are based on real-world experience, driving dynamics, actual fuel consumption, and mechanical reliability for used cars around four years old. Interestingly, both the Audi A4 (B9 generation facelift) and the BMW 3 Series (G20/G21 generation) saw a massive rollout of mild-hybrid (MHEV) technology for their popular two-liter engines during this period. This 48V or 12V system significantly smoothed out the operation of the often-dreaded start-stop system and contributed to unrivaled operating efficiency for both rivals. Although the market also offers top-tier six-cylinder engines, for the vast majority of buyers of used premium mid-size cars, the improved four-cylinder diesel engines make the most sense in terms of price, residual value, and reliability.

For the Audi A4, we recommend: 40 TDI (150 kW)

This two-liter turbodiesel (internally designated as EA288 evo) is the most sensible and popular choice in the A4 model hierarchy. Compared to the weaker 35 TDI version, it offers a noticeably better power reserve while maintaining practically identical running costs. Furthermore, in the 2020–2023 model years (B9 generation), the engine received more sophisticated mild-hybrid assistance.

• Why it's the best choice: It guarantees a great compromise between the purchase price of a used car, sufficient dynamics for a fully loaded family estate, and everyday efficiency. It is a reliable workhorse that doesn't suffer from serious teething problems and perfectly matches the character of a comfortable, stable touring car.
• Technical advantages: The torque curve, with a generous peak of 400 Nm, comes on very smoothly, and real-world fuel consumption during calm driving outside the city hovers around an impressive 5.0 to 5.5 l/100 km. The interplay with the seven-speed S tronic dual-clutch transmission is logical and refined in these model years thanks to software updates.
• Known risks and weaknesses: For cars around four years old, the main focus should be on the S tronic transmission and the diesel particulate filter (DPF).
• Who it's best for: For typical highway mile-munchers, families who often travel long distances, and drivers who spend a significant amount of time behind the wheel (more than 20,000 km per year).

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

The 320d engine, code-named B47, in the current G20 (sedan) and G21 (estate) generation is objectively one of the best four-cylinder diesel engines ever created by the automotive industry. While the much older N47 generations were sometimes haunted by timing chain issues, the modern B47 is an exceptionally reliable, refined, and mechanically robust unit.

• Why it's the best choice: The Bavarian "three-twenty-d" provides a beautifully linear pull, premium refined operation, and, above all, a perfectly seamless symbiosis with the fantastic eight-speed ZF automatic transmission with a torque converter. Among four-year-old diesel used cars, this combination has no driving competition on the market.
• Technical advantages: The engine utilizes sophisticated TwinPower Turbo technology, offering almost instantaneous throttle response and a thick 400 Nm of torque from very low RPMs. Real-world fuel consumption is often a few tenths lower than its Audi competitor – experienced drivers commonly average 4.8 l/100 km, which is a fascinating result for a car with rear-wheel (or even all-wheel) drive.
• Known risks and weaknesses: A truly significant enemy of this modern engine is carbon buildup in the intake manifold and issues with EGR valve clogging.
• Who it's best for: For dynamically oriented drivers, corporate managers, and everyone who demands the sporty handling characteristics of a rear-wheel-drive car and direct steering without having to make any compromises in fuel consumption on long trips.

Official fuel consumption figures provided by car manufacturers often become a hard-to-reach ideal in the real world, especially in the case of older or overly optimistic measurement methodologies. Actual operational efficiency depends primarily on driving style, route profile, and, last but not least, the actual load of the vehicle. To get the most accurate and objective picture possible, we relied on independent user data collected across Europe, primarily from the database of the crowdsourced portal Spritmonitor.de. Here, drivers have been carefully recording their refueling for a long time, allowing us to transparently compare how the most popular engines of roughly four-year-old used cars stand against each other – specifically premium representatives in the form of the Audi A4 (B9 generation) and the BMW 3 Series (G20/G21 generation).

Source:

When interpreting these numbers, a long-term trend typical for the premium mid-size class becomes quite clear – two-liter diesel engines still represent an absolute masterpiece of efficiency here. The Bavarian 320d model, despite its very respectable 140 kW output, achieves excellent average fuel consumption, easily keeping pace with the Audi 35 TDI engine, which is slightly weaker on paper, while offering a subjectively more powerful feel in terms of everyday dynamics. On the other hand, a slight surprise is hidden in the table for petrol units. The popular myth that modern turbocharged two-liter petrol engines nowadays drive for almost as much as diesel falls apart with these heavier family cars. For the more powerful Audi A4 40 TFSI version, the average for real users commonly climbs above the eight-liter mark. On the other hand, the BMW 320i, also thanks to its excellently tuned engine management and superb eight-speed gearbox, stays at a surprisingly reasonable 7.1 l/100 km, making it an exceedingly rational choice.

For a typical used car buyer, this brings clear recommendations. If you are a driver who regularly swallows hundreds of highway kilometers and is looking for a long-distance cruiser for frequent business trips or weekend trips to the seaside, the diesel engine remains an unmatched tool for saving the household budget. The particularly refined unit in the 320d or the slightly more modest 35 TDI will fulfill exactly what you expect from it. However, the situation is completely opposite for drivers who spend the vast majority of their time in the city and on shorter suburban routes. Here, petrol engines make clear sense – in such a regime, complex diesels with their DPF filters would suffer and actually lose all their consumption advantage through more expensive future servicing.

In the end, it can be said that fuel consumption will play a major role in deciding between the Audi A4 and the BMW 3 Series more when choosing your ideal engine, rather than as a direct deciding argument between these two rivals. Both manufacturers possess highly advanced technology, and for comparably powerful versions, the differences on the trip computer are at most in the range of tenths of a liter. Therefore, preferences regarding design, drive layout (front-wheel drive for Audi versus rear-wheel drive for BMW), or affinity for a specific brand will have a much greater say in the final selection.

Price Comparison on the Used Car Market

Both cars have long represented the most desirable options in the premium mid-size class. If we focus on roughly four-year-old cars (manufactured around 2022), we are comparing the popular Audi A4 generation (B9 after a significant facelift) and the BMW 3 Series (G20/G21 generation, both pre- and post-LCI facelift). BMW benefits from an overall newer basic architecture, while Audi offers proven and well-established technology on the market. This is logically reflected in used car prices, where BMW holds a slightly higher value.

Approximate Price Range (Four-Year-Old Cars)

Prices naturally depend on mileage, engine choice, and the attractiveness of the equipment (S line for Audi vs. M Sport for BMW). The following table shows common market prices for cars from approximately 2022 with a mileage of around 60,000 – 100,000 km on the Czech market.

(The prices listed are approximate for cars in very good condition with a documented service history).

Depreciation and Investment Value

• Audi A4 (B9): The B9 generation has been on the market since 2015, and although it underwent a very extensive exterior and interior modernization in 2019, its structural age contributes to a steeper depreciation curve. For buyers on the used car market, however, this is a major advantage – the Audi A4 often represents a more rational and affordable choice in terms of price/performance ratio.
• BMW 3 Series (G20): The Munich model entered the market in 2019 as a completely new generation. It boasts a more modern interior concept and more advanced driving assistants. Thanks to this and strong demand for driver-oriented cars, the price of used BMWs drops more slowly. Units equipped with xDrive and the popular M Sport package clearly hold their value best on the market.

What to Watch Out for During Servicing

When buying a premium mid-size car, it is necessary to keep in mind that although the purchase price has dropped by thousands compared to a new car, the prices of spare parts and labor rates in authorized service centers remain "premium."

• For Audi, it pays to carefully monitor the service intervals of the S tronic dual-clutch transmission (regular oil changes are recommended every 60,000 km at the latest) and check the functionality of the all-wheel-drive system (specifically the more efficient quattro ultra version with a connectable rear axle).
• For BMW, timely maintenance of the legendarily reliable ZF eight-speed torque converter transmission and the xDrive all-wheel-drive system is key, especially the transfer case (the so-called xDrive transfer box), which is sensitive to uneven tire wear.

Costs for common consumables such as brakes, shock absorbers, or tires are at very similar levels for both rivals.

Both premium models, the Audi A4 and the BMW 3 Series, boast a maximum five-star rating in safety tests by the independent organization Euro NCAP. When choosing a used car, however, it is crucial to put these results into the context of the time when the tests were actually performed.

Euro NCAP methodology and testing protocols constantly evolve and become significantly stricter over the years. Therefore, percentages obtained in different years cannot be directly compared. Modern protocols include more complex simulations of frontal and side impacts, stricter cyclist detection tests, and complicated intersection scenarios that older cars did not encounter at all during their tests. For this reason, the validity of the rating officially expires after about six to seven years.

The Audi A4 (B9 generation) underwent Euro NCAP crash tests in 2015. At the time, the car excelled with its rigid body and standard automatic emergency braking system (Audi pre-sense city), which monitored vehicles and pedestrians. However, the certification of this five-star result has formally expired due to the age of the test. It is worth noting that requirements for assistance systems and the protection of vulnerable road users were simply not as demanding in 2015.

The BMW 3 Series (G20 generation) was tested four years later, in 2019. The car thus had to face significantly tougher criteria. In this more modern context, a score of 97% for adult occupant protection is an extraordinary achievement, placing the Bavarian sedan at the top of its class. Furthermore, BMW benefited from a more sophisticated active hood and more advanced autonomous braking systems that react in detail to cyclists as well, which was positively reflected in the excellent rating for the protection of vulnerable road users.

In conclusion, both cars offer highly reliable occupant protection. However, the BMW 3 Series benefits from more recent engineering development and, in the market for 4-year-old used cars, represents a noticeably more modern and comprehensive safety package certified according to much stricter standards.

In addition to standard equipment, each model offers several unique features that can be decisive for the customer and clearly demonstrate the different approaches of both premium brands to detail and everyday use.

Audi A4: Technological Precision and Smart Efficiency

• Infotainment and Display: The Audi virtual cockpit plus digital instrument cluster has long been considered one of the best on the market. It stands out for its exceptional smoothness, high resolution, and the unrivaled ability to integrate detailed navigation maps directly into the driver's field of vision across the entire display.
• Advanced Lighting Technology: The top-of-the-line optional Matrix LED headlights can shade oncoming and preceding vehicles with incredible precision, allowing you to keep your high beams on at all times. The design icing on the cake is the dynamic indicators and impressive welcome light animations.
• Intelligent All-Wheel Drive: For many engine variants, the manufacturer uses the advanced quattro with ultra technology system. To save fuel, it lightning-fast mechanically disconnects the rear-axle drive when it's not needed (for example, during steady highway driving). Upon detecting a loss of traction, it reconnects within milliseconds, combining the benefits of an efficient front-wheel drive with the confidence of all-wheel drive.
• Predictive Assistance: The Efficiency Assistant system can read navigation data and recognize traffic signs. As a result, the vehicle automatically adjusts its speed before approaching curves, intersections, or town boundaries, significantly contributing to a smooth, safe, and economical drive.
• Acoustic Comfort: The A4 model prides itself on top-tier cabin soundproofing. In used cars, you will often find optional acoustic front windows that perfectly isolate the interior from wind noise even at high highway speeds.

BMW 3 Series: Innovative Assistance and Iconic Details

• Revolutionary Parking: The Reversing Assistant system is an extremely popular and practical feature. The car constantly remembers the last 50 meters driven (at speeds up to 36 km/h). If you accidentally drive into a narrow alley that you cannot exit forward, the car can reverse out completely on its own along the exact same trajectory.
• Control and Connectivity: The BMW iDrive system is among the absolute best in user-friendliness and ergonomics, especially thanks to the retention of the physical rotary controller on the center console. It also includes a smart voice assistant and, for these model years, fully supports over-the-air (OTA) software updates, allowing the vehicle to improve over time.
• Top-Tier Lighting Technology: As an upgrade to standard LED headlights, BMW often offers the highly sought-after BMW Laserlight on the used car market. They can be identified by the blue elements inside the headlights, and their adaptive high beam can illuminate the road up to an impressive distance of 530 meters.
• Smartphone Key: With the BMW Digital Key function, the car is unlocked, locked, and started simply by holding a compatible smartphone near it (via NFC technology). You can safely leave the physical key at home, and access to the car can be shared electronically with other users.
• Genius Details of the Touring Version: The estate variant retains the traditional Bavarian feature of an independently opening rear window. You will appreciate this when quickly tossing smaller items into the trunk, or in tight garages where the entire tailgate cannot be opened. In the luggage compartment of better-equipped models, you can find unique rubberized anti-slip rails that rise slightly after the tailgate is closed, preventing cargo from sliding around the trunk.

The Audi A4 is the perfect choice for drivers who demand maximum refinement, top-notch craftsmanship, and seamless highway comfort from their car. It will appeal to rational buyers who prefer understated premium elegance and unshakable stability over sporty antics on winding backroads.

The BMW 3 Series (G20 generation) has long been considered the benchmark for driving experience in the mid-size class and is tailored for those who want to actively enjoy driving. It offers an unrivaled connection between machine and driver, excellent ergonomics, and modern technology, albeit at the cost of slight compromises in overall ride comfort on poor roads.

Based on our own statistics, service reports, owner feedback, and results from comprehensive car inspections, we have compiled an overview of the most common problems that buyers of approximately four-year-old used cars of these models should watch out for.

Audi A4 generation B9 (post-facelift) is considered a very solid and sturdily built car, yet specific defects appear that are worth checking thoroughly during selection.

• Infotainment and electronics: With the MMI system, owners often complain about occasional screen freezing, slower responses, and connection drops via Apple CarPlay or Android Auto. In most cases, installing the latest software update at an authorized service center helps.
• Engine and cooling: In the highly sought-after 2.0 TDI diesel engines, coolant leaks may occur due to a leaking water pump. Furthermore, failures of AdBlue system sensors (NOx sensors) are reported, which manifests as an error message on the instrument cluster.
• Transmission (S tronic): Seven-speed dual-clutch transmissions are sensitive to neglected maintenance. If the oil change interval (usually every 60,000 km) is not followed, they can suffer from jerking when starting, downshifting, or more expensive mechatronics failures. In these cases, a physical inspection of the used car combined with a test drive is absolutely crucial.
• Chassis: Due to the more complex multi-link front axle, cars with higher mileage experience faster wear of the control arm bushings. The problem most often manifests as a dull knocking from the front wheels when driving over bumps.

BMW 3 Series (generation G20/G21) pleases with excellent workmanship and robust power units, however, even this popular premium model has its weak points, especially in the area of electronics and specific engine parts.

• Engine and exhaust system: In popular diesel engines (such as the 320d version), it is necessary to watch out for the exhaust gas recirculation cooler (EGR valve). Coolant leakage and its mixing with soot can occur here, which the manufacturer often addressed within official recall campaigns.
• Steering and chassis: Owners of some used units report clicking or distinct knocking in the rack and pinion steering. The sound is most often heard when turning the steering wheel while stationary or when maneuvering at low speeds.
• Body and exterior: A known and relatively common defect is the failure of the active grille shutter actuator (the so-called kidney grilles). The system remains stuck in the open or closed position, resulting in the engine warning light coming on the dashboard.
• Electronics and interior: Software errors of the iDrive onboard system, such as black screens or freezing functions, are no exception and often relate to unsuccessful "over-the-air" updates. Occasionally, creaking of interior plastics also occurs. Before the final decision, an independent technical inspection of the car is always recommended, which will reveal hidden error codes in the fault memory.

When buying a used car, a thorough inspection is key. Here are some specific points to focus on for these two popular premium models. A professional used car inspection before making a final decision can save you a lot of worry and unexpected expenses for future repairs.

When choosing an Audi A4:

• S tronic (DSG) transmission: Focus on the smoothness of starting from a standstill and behavior when crawling in traffic. Jerking, hesitation during acceleration, or reluctance to downshift smoothly can indicate worn clutches or upcoming mechatronics issues. Thoroughly check the service history – the transmission oil must be changed at least every 60,000 km.
• Front axle and chassis: During the test drive, intentionally drive over several bumps, potholes, or speed bumps. The complex multi-link front axle can suffer from play in the control arm bushings after years. These most often manifest as squeaking or a dull thumping transmitted to the floor.
• MMI Infotainment: Test all functions of the onboard system. In post-facelift models, the screen can occasionally freeze, reactions after startup can be very slow, or Bluetooth connections can drop. Check if the system shows lag and find out if the latest software version is installed in the car.
• Coolant leaks and cold starts: In the popular 2.0 TDI and 2.0 TFSI engines, leaks can appear around the water pump and thermostat housing. Check the coolant level and, after a cold start, listen carefully to whether the engine runs smoothly without fluctuating RPMs or unwanted metallic clicking.

When choosing a BMW 3 Series:

• Steering and front axle: In the G20 generation, hidden knocking from the steering rack occasionally appears. Try turning the steering wheel quickly from side to side while stationary with the engine running – there should be no metallic sounds or noticeable play. An independent technical inspection of the car's condition will reliably help reveal these potential chassis defects.
• ZF automatic transmission: The classic eight-speed automatic should shift completely smoothly and intuitively under all circumstances. If it downshifts hard when approaching an intersection or hesitates noticeably when the gas is suddenly pressed, it could be due to neglected transmission oil maintenance or a need for a software reset and update.
• Battery condition for plug-in hybrids (330e): If you are considering an electrified version, check the estimated electric range at full charge on the trip computer. A significantly reduced value may indicate accelerated degradation of the high-voltage battery, while the real range for a four-year-old unit should be around 40 km depending on conditions.
• Brake condition (M Sport): If the car is equipped with optional M Sport brakes (easily recognizable by the large blue calipers), thoroughly check the edge of the discs and the remaining thickness of the pads. They are characterized by strong braking performance but tend to wear out faster, and their complete replacement is quite expensive.
• iDrive 7 system operation: Check the smoothness of the digital instrument cluster and the main central display. Try navigating through the menus quickly – the system must not freeze, restart (so-called black screen), and the wireless phone connection via Apple CarPlay or Android Auto must start reliably and without dropouts.

Sources: ADAC, aktualne.cz, lidovky.cz, elektromobil.cz, techfocus.cz, retroauta.cz

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