BMW S85B50 engine code explained
S85B50 is the full code for BMW's only production V10, the 5.0-litre naturally aspirated engine in the E60 M5 saloon, E61 M5 Touring and E63 / E64 M6 of 2005 to 2010. It makes 500 bhp at 7,750 rpm, drives through the SMG III single-clutch gearbox (or a rare manual in the US), and carries the best-known rod-bearing and throttle-actuator reputation of any BMW engine.
Quick answer
The S85B50 is the 5.0-litre V10 naturally aspirated M engine petrol of the BMW S85 family, built 2005-2010. Bimmer.AI scores the family 6 / 10: a sound used buy provided the known weak points are documented. The tables below give every output tier and sticker letter BMW used on this stem and which cars got them; the failure table is the same one that powers the S85 family guide.
How to read S85B50
| Part of the code | Meaning |
|---|---|
| S | BMW M GmbH (M Division) engine |
| 85 | engine family number within the S-series |
| B | petrol, longitudinal (rear-drive platform: 1 to 8 Series, X3 to X7, Z4) |
| 50 | displacement in tenths of a litre: 5.0 litres |
| K / U / M / O / T / S + digit | output tier and revision, appended in BMW's internal naming (for example S85B50O1) |
| A / B / C / D | parts-catalogue engine version printed on the engine cover sticker (for example S85B50A) |
S85B50 output tiers and which cars have them
| Code | Output | Cars | Notes |
|---|---|---|---|
| S85B50 | 500 bhp | M5 (E60 2005-2010), M5 Touring (E61 2007-2010), M6 (E63 / E64 2005-2010) | Single tier |
S85B50 sticker letters: S85B50A
One letter, one engine. The buyer checklist is rod bearings (£2,000 to £3,500 at 50,000 to 70,000 miles, non-negotiable without receipts), the two throttle actuators (£1,000 to £2,000 for the pair), VANOS oil pump and high-pressure lines, and the SMG hydraulic pump. With all of that documented an S85 car is one of the great used performance bargains; without it, budget £5,000 before you enjoy it.
| Sticker code | What it denotes |
|---|---|
| S85B50A | Standard parts-catalogue version for M5 and M6. |
Known problems on every S85B50
Failure data is held once, per engine family, so this table is identical to the BMW S85 guide. Cost ranges are indicative UK figures.
| Failure mode | Severity | Frequency | Typical onset | UK repair range |
|---|---|---|---|---|
| Rod bearing wear | Catastrophic | Very common | 40 to 90k mi | £2,000 to £3,500 |
| Throttle actuator failure (10 individual units) | Moderate | Very common | 30 to 100k mi | £300 to £2,500 |
| VANOS solenoid weep (two units, one per bank) | Moderate | Common | 60 to 130k mi | £400 to £700 |
| SMG hydraulic pump failure (SMG cars only) | Serious | Common | 60 to 130k mi | £600 to £1,200 |
| Coolant pump and thermostat | Moderate | Common | 60 to 130k mi | £500 to £800 |
Long-term verdict
Pinnacle of naturally aspirated BMW M engineering: 507 bhp from 5.0 litres at 8250 rpm, F1-derived thinking. Also one of the highest-maintenance engines BMW has sold. Rod bearing replacement at 60-80k miles is mandatory (£2,000 to £3,500). 10 throttle actuators. SMG hydraulic pump on most cars (£600 to £1,200). Genuinely a specialist car; E60 M5 prices reflect this.
Check a specific S85B50 listing
Paste any BMW S85 listing, VIN or registration. Bimmer.AI identifies the exact engine and returns the buyer report in 30 seconds.
Run a Bimmer.AI buyer report →Bimmer.AI is designed to help you identify BMW-specific buyer risks before you travel, negotiate, or pay for an inspection. It does not replace a physical inspection by a qualified mechanic, a legal vehicle-history check (e.g. HPI Check), or independent verification of finance, stolen, or write-off status. Repair-cost ranges are indicative UK figures that vary by region, specialist, parts supply, and labour rates.
Frequently asked questions
Why are S85B50 rod bearings such a big deal?
The S85 runs very tight bearing clearances and thin oil, and the original lead-copper bearings wear measurably by 50,000 to 70,000 miles. Left alone the bearing spins and the engine is scrap. Replacement with revised bearings and bolts is £2,000 to £3,500 at an M specialist and is treated as a scheduled service by the community. Ask for the invoice before anything else.
Which cars have the S85B50?
Only the E60 M5 saloon (2005 to 2010), the E61 M5 Touring (2007 to 2010, around 1,000 built) and the E63 M6 coupe and E64 M6 convertible (2005 to 2010). The same architecture minus two cylinders became the S65B40 in the E9x M3.
Which BMWs have the S85B50 engine?
The S85B50 went into the following cars, by output tier. S85B50 (500 bhp): M5 (E60 2005-2010), M5 Touring (E61 2007-2010), M6 (E63 / E64 2005-2010). The two-letter family badge is S85; any listing that quotes the family code is talking about one of these.
Is the BMW S85B50 reliable?
Bimmer.AI scores the S85 family 6 out of 10, which makes the S85B50 a sound used buy provided the known weak points are documented. Pinnacle of naturally aspirated BMW M engineering: 507 bhp from 5.0 litres at 8250 rpm, F1-derived thinking. Also one of the highest-maintenance engines BMW has sold. Rod bearing replacement at 60-80k miles is mandatory (£2,000 to £3,500). 10 throttle actuators. SMG hydraulic pump on most cars (£600 to £1,200). Genuinely a specialist car; E60 M5 prices reflect this.
What does S85B50 mean?
S is the BMW M GmbH (M Division) engine, 85 is the family number, B means petrol, longitudinal (rear-drive platform: 1 to 8 Series, X3 to X7, Z4), and 50 is the displacement in tenths of a litre (5.0 litres). BMW appends an output tier and revision (K, U, M, O, T or S plus a digit) in its own naming, and the parts catalogue adds a version letter (A, B, C) that is what you see on the engine cover.