Which BMW 3 Series Is the Most Reliable? Full Engine Comparison

 Photo by Niek van Ark on Unsplash

If you're looking to buy a BMW 3 Series or already own one, you’re probably wondering which engine will give you the best long-term reliability. In this detailed comparison, we’ll dive into BMW 3 Series engines. From petrol and diesel engines, we will try to cover which ones consistently deliver durability, performance and peace of mind. We’ll also touch on what to watch out for and and will rank the most reliable BMW engines and which cars have them. Let’s dive deep. 

What Makes a BMW Engine Reliable?

Before we look at specific models, reliability isn’t just about “how many miles it makes.” The best BMW engines:

• Have a robust design with durable components (e.g., chain vs belt, cooling system efficiency)
  
  

• Are simple enough to maintain well, without overly complex systems that tend to fail
  
  

• Are supported by good BMW parts availability and experienced service networks
  
  

• Show proven performance over large sample sizes (many units, varied driving styles, etc.)

BMW 3 Series Generations and Engines

This table highlights the evolution of BMW 3 Series engines, from simple petrol fours and sixes in early generations to the robust M54/M57 era, and finally to today’s turbocharged modular B-series engines with modern efficiency and hybrid options.

Generation	Petrol Engines	Diesel Engines
E21 (1975-1983)	M10 (I4), M20 (I6)	—
E30 (1982-1994)	M10, M40 (I4), M42 (I4), M20 (I6), S14 (I4 in M3)	M21 (I6)
E36 (1990-1999)	M40/I4, M42, M44, M50, M52, etc.	— (or early I4 diesels in some markets)
E46 (1997-2006)	M43, N42, N46 I4; M52/M54/S54 I6	M47 I4; M57 I6
E90 / E9x (2004-2013)	N45, N46, N52, N53, N54, N55 I4 & I6 petrol; also higher-performance like S65 V8 in M3	M47, N47 I4 diesels; M57 / N57 I6 diesels
F30 (2011-2018)	N13, N20, N55, B38, B48, B58 I4 & I6	N47, B47 I4; N57 I6 diesels
G20 (2018-present)	B48, B58, S58 I6; petrol plug-in hybrid versions	B47 I4; B57 I6 diesels

Ranked: The Most Reliable BMW 3 Series Engines (2004 → Present)

Here’s how we would rank every major 3 Series engine from the last two decades, from the strongest bets to the ones you’ll want to research twice before buying.

Rank	Engine Code	Models (3 Series)	Pros	Cons
1	M57 (Diesel I6)	E90/E91/E92 330d, 335d (2005–2012)	Legendary reliability, huge torque, 300k+ miles capable	Swirl flaps, EGR, injector wear
2	B58 (Petrol I6 turbo)	F30 340i (2015–2018), G20 M340i (2019–present)	Modern, robust, smooth, award-winning	Turbo/injector failures are costly
3	N52 (Petrol I6 NA)	E90/E91/E92 323i, 325i, 330i (2005–2013)	No turbo, smooth & durable	Water pump failures, oil leaks
4	B57 (Diesel I6)	G20 330d, 340d (2019–present)	Efficient, powerful, refined	DPF/AdBlue/EGR failures are costly
5	N55 (Petrol I6 turbo)	E90/E92 335i (2009–2013), F30 335i (2012–2015)	Stronger reliability than N54	HPFP & injector issues
6	B47 (Diesel I4)	F30/F31/F34 318d, 320d (2015–2018), G20 318d, 320d (2019–present)	Efficient, improved timing chain vs N47	Still some N47 engine problems
7	B48 (Petrol I4 turbo)	F30/F31 320i, 330i (2015–2018), G20 320i, 330i (2019–present)	Decent reliability, efficient	Turbo & timing chain tensioner issues
8	N54 (Petrol I6 twin-turbo)	E90/E92 335i (2006–2010)	Exciting, tunable	HPFP, turbo, carbon build-up
9	N20 (Petrol I4 turbo)	F30/F31/F34 320i, 328i (2012–2015)	Light, fuel-efficient	Timing chain & turbo wear
10	N47 (Diesel I4)	E90/E91/E92 318d, 320d (2007–2012); F30/F31/F34 316d, 318d, 320d (2012–2015)	Efficient, common	Catastrophic timing chain failures
11	B38 (Petrol I3 turbo)	F30/F31 318i (2015–2018), G20 318i (2019–present)	Fuel economy, lightweight	Stressed, not long-life
12	S65 / S55 / S58 (M engines)	E90 M3 (S65 V8, 2007–2013); F80 M3 (S55 I6 turbo, 2014–2018); G80 M3 (S58 I6 twin-turbo, 2020–present)	Motorsport pedigree, thrilling	Very high maintenance & running cost

The Standout Choices

• Best overall diesel: The M57. It’s a workhorse — simple by today’s standards, extremely durable and capable of very high mileage.
  
  

• Best modern petrol: The BMW B58 Engine. It’s won multiple awards for its balance of power, refinement and dependability.
  
  

• Best naturally aspirated petrol: The N52. If you want a simple, smooth six-cylinder with fewer things to break, this is it.

Engines to Approach with Caution

• N47 (2.0 diesel): notorious for timing chain failures. Repairs often mean a full BMW engine replacement, which is why many buyers avoid early N47s altogether.
  
  

• N20 (2.0 petrol): efficient but has timing chain and turbo issues, not a long-life motor unless it’s been fully fixed.
  
  

• N54 (3.0 twin-turbo petrol): loved for its performance and tuning potential, but plagued with high-pressure fuel pump failures, turbo wear and carbon build-up.

Why Gearbox Matters Too

Well, in this article we mainly compared engines, but usually, it’s not just about the engine, even it’s the main component of the car. BMW gearboxes, especially automatics paired with high-torque diesels, are a great choice. A BMW gearbox replacement can cost thousands. The three best BMW gearboxes are the ZF 8HP automatic (smooth, reliable, used in F30/G20 3 Series), the Getrag 6-speed manual (durable and engaging, found in E90/E92) and the older ZF 6HP automatic. Before buying the car, always check service history: fluid changes, clutch/DMF health (manuals) and smooth shifting are key to long-term reliability.

Final Thoughts: Which 3 Series Is the Most Reliable In Our Opinion?

If you’re buying today and want the least headaches:

• Choose a 3 Series with the M57 (diesel) if you don’t mind an older car and want bulletproof torque.
  
  

• Go for a B58 (petrol) if you want something modern, smooth and powerful.
  
  

• The N52 remains a safe bet for those who prefer naturally aspirated simplicity.
  
  

The newer B-series engines (B47, B48, B57) are good, but they bring modern emissions complexity that makes them more expensive to run long-term. The older N47 and N20 engines are best avoided unless you know their weak points have already addressed after over 150,000 miles.

At the end of the day, the most reliable BMW 3 Series is the one with a proven engine, full service history and careful previous owners. Choose wisely and the 3 Series really will live up to its reputation as the “Ultimate Driving Machine.” And if you’re buying a newer model, BMWs are reliable cars, just be sure to look after it properly and stick with genuine BMW parts.

Disclaimer: This article is intended for general information only. Engine reliability rankings are based on widely reported owner experiences, service data and our insights. Actual reliability will vary depending on each car’s age, mileage, service history, and driving conditions. Always conduct a professional inspection and verify the maintenance records before purchasing any BMW.