Mercedes-Benz has built a strong reputation for premium engineering, smooth performance, and long-lasting engines. Many of its power units are known to cover extremely high mileages with proper care, especially when maintained with high-quality Mercedes-Benz engine oil UK. These engines power everything from compact models such as Mercedes-Benz A-Class engines and CLA engines, to executive saloons like Mercedes-Benz C-Class engines and E-Class engines, all the way up to large vans such as Mercedes-Benz Sprinter engines and Vito engines.
Interest in the brand continues to rise, especially with the growing demand for new Mercedes-Benz models in the UK and the upcoming Best Mercedes-Benz series 2025. Whether you’re buying a used Mercedes, searching for a used engine, or exploring reconditioned engine options through specialists like Engine Finders, knowing which engines are reliable and which ones cause trouble is essential.
Below you will find the top twenty most dependable Mercedes-Benz engines, followed by twenty that are best avoided.
Comparison Table: 20 Best vs 20 Worst Mercedes Engines
| Most Reliable Mercedes Engines | Engines to Avoid |
| M113 V8 | M272 V6 (early years) |
| M112 V6 | M273 V8 (early years) |
| OM617 Diesel | OM642 (early) |
| OM606 Diesel | M156 AMG (pre-update) |
| OM648 Diesel | M278 Biturbo V8 |
| M104 Inline Six | M276 V6 |
| M119 V8 | M271 Kompressor |
| M156 AMG (updated) | M266 Turbo variants |
| M270/M274 (updated) | Early M274 |
| M178 AMG 4.0 Biturbo | OM651 (early years) |
| OM642 (revised) | Late M104 wiring issues |
| M103 | M111 Supercharged |
| M102 | Early emissions M102 |
| OM651 (updated) | Early M264 |
| M273 (updated) | M281 |
| M264 (recent) | M282 1.3 Turbo |
| M137 V12 | OM640 Diesel |
| M266 | Emissions-heavy OM651 |
| M254 | M166 (early A-Class) |
| M256 Inline Six | Early M119 (bad wiring) |
The 20 Most Reliable Mercedes-Benz Engines
Here are the Mercedes engines most praised for long-term reliability, smooth performance, and minimal failure rates.
1. M113 V8
Well known for powering the CLS, S-Class, SL, and certain G-Class engines, the M113 is regarded as one of Mercedes’ greatest achievements. It is durable, simple in design, and delivers impressive longevity when maintained with proper servicing.
2. M112 V6
Used widely in older C-Class, E-Class, CLK, and SLK engines, the M112 is a dependable six-cylinder unit known for smooth operation and low running costs.
3. OM617 Diesel
This engine earned a legendary reputation for its million-mile potential. Seen in older G-Class and E-Class models, it remains one of the toughest diesel engines ever built.
4. OM606 Diesel
Another icon among diesel engines. It is highly sought after for conversions and performs brilliantly in heavy vehicles, including older Vito engines and Viano engines.
5. OM648 Diesel
Well loved in early-2000s E-Class models, this inline-six diesel delivers excellent refinement and strong long-term reliability.
6. M104 Inline Six
Known for its smooth power delivery and strong build. Found in older C-Class, E-Class, and SL engines.
7. M119 V8
A durable, high-performance V8 found in older luxury models such as the S-Class and SL.
8. M156 AMG V8 (updated version)
Once the head bolt and valve train issues were corrected, the M156 became one of AMG’s most reliable engines. It appears in SLS AMG engines, C-Class AMG, and various E-Class AMG models.
9. M270 / M274 (later revisions)
These engines power A-Class, B-Class, CLA, and GLA-Class engines. The updated versions resolved early timing problems.
10. M178 AMG 4.0 Biturbo
This engine is the heart of the Mercedes-Benz AMG GT engines. It combines incredible performance with excellent reliability.
11. OM642 Diesel (revised version)
A popular diesel option in ML-Class engines, GL-Class, GLS engines, R-Class, and Sprinter engines.
12. M103 Inline Six
A durable, simple engine used in classic Mercedes saloons and coupes.
13. M102 Inline Four
Straightforward, reliable, and found in many earlier compact models.
14. OM651 Diesel (updated)
An improved design that powers vehicles like the Citan engines, V-Class engines, and GLA-Class. The updated model is far better than its early version.
15. M273 V8 (updated balance shaft)
Reliable, smooth, and strong once the balance shaft issue was resolved. Found in S-Class, CLS, and E-Class engines.
16. M264 Turbo Four
A newer and more efficient petrol engine used in the latest C-Class, GLA, CLA, and GLC-Class engines.
17. M137 V12
A robust V12 that performs well when cared for, usually seen in older flagship saloons.
18. M266 Inline Four
A solid engine used in first-generation A-Class and B-Class models.
19. M254 Mild Hybrid
This new-generation engine shows excellent early reliability, with smooth hybrid integration.
20. M256 Inline Six
Found in modern S-Class, GLS, and GLE engines, this inline-six combines luxury refinement with strong dependability.
20 Mercedes-Benz Engines To Avoid
These engines are known for design flaws, high repair bills, or early failures.
1. M272 V6 (early years)
Early versions suffer from balance shaft failures. Common in older C-Class, E-Class, and CLS engines.
2. M273 V8 (early years)
Timing issues and balance shaft problems make this V8 risky.
3. OM642 (early models)
Swirl flap and oil cooler leaks were common before the redesign.
4. M156 AMG (pre-update)
Head bolt faults and valve train failures plagued early versions.
5. M278 Biturbo V8
Heat-related problems and oil leaks make this engine expensive to maintain.
6. M276 V6
Often found in GLC-Class engines, C-Class, and E-Class, this V6 suffers from timing chain stretch and carbon build-up.
7. M271 Kompressor
Timing chain tensioner failure is a common and costly issue.
8. M266 Turbo Variants
Turbocharged versions run hot and are less reliable than their standard counterparts.
9. Early M274 Turbo
Oil consumption and timing issues are common in the first production years.
10. OM651 Early
Early versions suffered from injector failures and timing problems.
11. Late M104 with biodegradable wiring
The wiring harness deteriorates, leading to unpredictable electrical faults.
12. M111 Supercharged
Supercharger clutch wear and bearing problems appear early.
13. Early emissions-era M102
Weak timing components cause reliability issues.
14. Early M264
Cooling and sensor issues affect early production models.
15. M281
This engine suffers from oil usage and limited durability.
16. M282 1.3 Turbo (Renault-based)
Frequently criticised for poor long-term reliability.
17. OM640 Diesel
Injector and turbocharger problems are common.
18. Emissions-heavy OM651
Overloaded with emissions systems that often fail.
19. M166 (early A-Class)
Subframe design flaws affect engine mounting stability.
20. Early M119 with faulty wiring
The early biodegradable wiring causes long-term problems, despite the engine’s strong core design.
How to Pick a Reliable Mercedes Engine
Choosing the right engine matters whether you’re buying a complete car or replacing a unit with a used engine, reconditioned engine, or OEM car engine.
1. Always check the service history
Full records matter more than mileage, especially for S-Class, GLE, GLC, and C-Class engines.
2. Look for proof of timing chain replacements
Some engines have known timing problems and require early intervention.
3. Avoid engines with heavy oil leaks
Always use the correct Mercedes-Benz engine oil UK to protect longevity.
4. Listen for unusual engine noise
A healthy Mercedes engine should run smoothly and quietly.
5. Inspect the cooling system
Overheating shortens engine life dramatically.
6. Get a Quote
Before replacing your engine, always get a quote from trusted suppliers like Engine Finders, who offer reliable used engines and reconditioned engines at competitive prices.
Conclusion
Mercedes-Benz has built some of the most reliable engines the world has ever seen. Many appear in popular UK models such as the G-Class engines, GLA-Class, GLC-Class, E-Class, C-Class, and S-Class. These dependable engines can deliver hundreds of thousands of miles when properly maintained.
At the same time, some engines are best avoided due to design flaws or expensive long-term problems. Knowing the difference helps you choose the right Mercedes, whether you’re buying a car or replacing an engine.
FAQs
1. What is the most reliable Mercedes engine ever made?
The M113 V8 is widely regarded as the most reliable Mercedes-Benz engine, known for exceptional longevity and minimal failures.
2. Which Mercedes engines should I avoid when buying used?
Avoid early M272 and M273 engines due to balance shaft issues, and early OM651 and OM642 diesels due to injector and swirl flap problems.
3. Are Mercedes diesel engines reliable in the UK?
Yes, engines like the OM617, OM606, and OM648 are known for exceptional durability and handle UK driving conditions well.
4. What Mercedes engine lasts the longest?
The OM617 diesel is famous for reaching over 500,000 miles, and many survive over a million miles with proper maintenance.
5. Which Mercedes engine is best for motorway driving?
The OM648 diesel and M256 inline-six are both excellent for long-distance cruising thanks to strong torque and fuel efficiency.
6. Are reconditioned Mercedes engines worth buying?
A high-quality reconditioned engine from a trusted supplier is a smart choice and can be more reliable than a high-mileage used engine.
7. What oil should I use for Mercedes engines in the UK?
Use approved Mercedes-Benz engine oil UK, typically 5W-30 or 5W-40, depending on the engine and climate. Always follow the handbook.
8. Do Mercedes timing chains last a long time?
Some engines have lifetime chains, but others like early M274, M276, and M271 require earlier inspection or replacement.
9. Which Mercedes engine is best for towing?
The OM642 diesel and M256 inline-six are excellent towing engines with plenty of torque.
10. Where can I get a replacement Mercedes engine in the UK?
You can get a quote from suppliers like Engine Finders, who offer used engines, reconditioned engines, and low-mileage imports for all Mercedes models.
