There's a well-worn phrase among Mercedes people: they don't build them like the M113 anymore. The data backs it up almost cruelly. The M113 V8 family is one of the most durable engines Mercedes ever made. The M273 that replaced it is a smooth, strong V8 too — but its early engines carry a soft idler gear in the timing drive that costs thousands to fix. If you're shopping a used V8 S-Class or E-Class, this is the comparison that matters.
Quick answer: Buy the M113 (89/100, BEST) — the AMG-era V8 that runs forever. Approach the M273 (66/100, CAUTION) with care: on engines up to serial 2739..30 088611 (built to about autumn 2006) the idler gear in the timing drive wears out — a US class-action defect and a €2,480–3,480 workshop job. Check the engine number; later engines got a hardened gear.
The one that lasts
M113 — 89/100 (BEST)
The M113 V8 (1997–2010) is the definition of over-engineered. Its one real mechanical watch-item is the harmonic balancer; the rest is age-related housekeeping, not design flaws:
| Problem | Severity | Repair cost |
|---|---|---|
| Harmonic balancer (crank pulley) rubber delaminates | High | €280–650 |
| Air suspension / Airmatic (S/ML models) | Moderate | €600–2,000 |
| Oil leaks — valve covers, rear main seal | Moderate | — |
| Crankshaft position sensor fails when hot | Minor | €50–125 |
| Spark plugs + ignition coils | Minor | €200–500 |
The Airmatic cost is a chassis item, not the engine — the block itself is famously indestructible, which is why tuners still build on the M113 today. Keep the maintenance up and it outlives everything around it. (Its V6 sibling, the M112, now has its own page and scores 84/100.)
Found in: Mercedes CLK 500, E 430/E 500, S 430/S 500, SL 500, ML 430/500, and the supercharged E55/C55/SL55 AMG.
The one to check by engine number
M273 — 66/100 (CAUTION)
The M273 (2005–2015, 4.7 and 5.5 litres) replaced the M113 in the big cars. Its one big weakness is confined to early production:
| Problem | Severity | Repair cost |
|---|---|---|
| Idler gear wear in the timing drive (engines up to serial 2739..30 088611) | Critical | €2,480–3,480 |
| Intake manifold flap lever breakage | Moderate | — |
| Camshaft adjuster solenoid / seal oil leaks | Minor | — |
| Map-controlled thermostat failure | Minor | — |
| Oil consumption at high mileage (from about 160,000 km) | Minor | — |
| Spark plugs + ignition coils (8 of each) | Minor | €400–900 |
The idler gear was made of insufficiently hardened sintered steel: the chain wears its teeth away, the cam timing drifts, and you get codes P0016/P0017, misfires and rattle at idle, typically at 80,000–150,000 km. Mercedes-Benz USA settled a class action with a sliding-scale warranty extension. It is a different part from the M272 V6's balance-shaft sprocket. The gear can be replaced in the car, though many workshops remove the engine; a German workshop quotes €2,480–3,480 including the chain set and tensioner. Engines built after about autumn 2006 have the hardened gear.
Found in: Mercedes S 500, E 500, CLS 500, SL 500, ML/GL 500, G 500.
Old vs new
| M113 | M273 | |
|---|---|---|
| Era | 1997–2010 | 2005–2015 |
| Score | 89/100 | 66/100 |
| Verdict | BEST | CAUTION |
| Defining trait | Indestructible block | Soft idler gear on early engines |
The verdict
This is the rare case where the older engine is the safer buy. The M113 is a modern classic you can run for decades. The M273 is a reasonable buy once you know which one you have: ask for the engine number before viewing — up to 2739..30 088611 means the soft gear unless an invoice shows it was replaced; later engines are far safer. Either way, get a specialist inspection first.
For the same "new isn't always better" story in Mercedes diesels, see OM651 vs OM654.
Scores are calculated from documented issues, repair costs, and failure patterns. Reviewed by the EngineScope editorial team. Methodology →