M Division's first 6 Series — the M88-engined coupe that bridged the M1 and the modern M cars.
The M635CSi (sold in North America from 1987 as the M6) was BMW M Division's first 6 Series. Power came from a development of the M88 inline-six first seen in the M1 — a 3,453cc DOHC unit with individual throttle bodies producing 286 bhp in European specification (256 bhp in US-market M6 with catalysts). The car combined the elegant Paul Bracq-supervised E24 body with M-Sport suspension, larger brakes and an M-specific interior including a dog-leg 5-speed manual gearbox.
Production across the 1984–1989 model years totalled approximately 5,855 European M635CSi plus 1,767 North American M6 — the M635CSi/M6 is the rarest of the four-seat M cars of its era.
First M-badged grand tourer; the direct evolution of the M1 powertrain into a usable four-seat car.
| Variant | Years | Production | Notes |
|---|---|---|---|
| M635CSi (Europe) | 1984–1989 | 5,855 | M88/3 engine, 286 bhp. |
| M6 (USA) | 1987–1989 | 1,767 | S38B35 with catalysts, 256 bhp. |
Start with identity, paperwork and originality. For the BMW M635CSi (E24), the strongest cars have continuous ownership history, matching numbers where applicable, original books and tools, factory build documentation and evidence of work by manufacturer-approved specialists. Original paint, original M88/3 engine numbers, full BMW service history, no accident damage.
M88/3 is a robust engine when properly maintained; throttle-body synchronisation, valve clearance checks and timing chain condition are the key items. A proper pre-purchase inspection includes cold-start behaviour, ECU diagnostics and fault-code history (where applicable), leak-down or compression testing, underbody photography, suspension and chassis inspection, brake condition and a long enough road test to expose heat-related faults. Deferred maintenance on a car of this class is almost always more expensive than buying a better-sorted example.
Use a paint-depth gauge, lift access and a specialist familiar with the model's factory panel gaps and finish standards. Collector value is dramatically affected by structural repairs, refinished panels, poor paintwork and missing factory trim or option content. Documented cosmetic refresh is acceptable; concealed accident or fire damage must be priced severely.
Original European M635CSi with M88/3 engine and dog-leg manual is the most desirable; matching numbers and original paint are critical. Specification, colour, options and limited-build variants move values significantly. Buy the best-documented example in the most desirable specification you can justify, rather than a tired example of a rarer derivative that will need years of corrective work.
| Date | Auction | Car | Mileage | Result |
|---|---|---|---|---|
| 2025-06-25 | H&H Classics UTAC Millbrook, Lot 56 | 1988 M635 CSi | — | £41,062 Sold |
| 2025-05-17 | Iconic Auctioneers The Iconic Sale at Supercar Fest, Lot 811 | 1986 M635 CSi | — | £40,500 Sold |
| 2024-11-08 | Osenat Epoqu'Auto: Youngtimers, Lot 31 | 1984 M635 CSi | — | €43,800 Sold |
| 2023-11-09 | Mecum Las Vegas 2023, Lot F169 | 1988 M6 (US) | — | $46,200 Sold |
First M Division grand tourer; M88-engine pedigree; rust-free supply diminishing.
Our view, not advice. This section is Car Collector International's editorial judgement on where this model sits in the collector market, based on the production, specification and market data set out in this guide. It is not a recommendation to buy or sell and it is not investment advice. Values can fall as well as rise.
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The valuation figures in this guide are for research purposes only and do not constitute financial or investment advice. See our full disclaimer.
