Used car buying guide: BMW M6

Launch control permits even more rapid starts but cooks the clutch and strains the rear differential. At least private-sale cars give you the opportunity to meet the owner and gauge their level of hooliganism.

Features include electronic damper control (EDC), which offers three ride settings. The model was facelifted in 2007, when it gained smarter lighting and a mildly reworked cabin. The M6 coupé outnumbers the cabriolet by two to one. The drop-top’s hood is a complex, high-quality affair, but although the body is stiffened where it matters, ultimately the model lacks the coupé’s poise and bite.

Whichever bodystyle you’re tempted by, aim to buy the best-serviced and best-equipped one you can afford; one that stands out from the crowd. That way, you’ll make the most of the emerging interest in naturally aspirated motors such as the M6’s stupendous V10.

How to get one in your garage

An expert's view

Jack Day, Sutherland M Power Cars: “We buy and sell all types of M car but I can’t remember when we last had an M6 in the showroom. It’s the unreliable SMG gearbox that bothers people. It’s not like today’s twin-clutch transmissions. It’s a peculiar thing, and when it goes wrong, it can be expensive. Putting a warranty on the model is another big expense. And I’d be wary of the convertible for the extra complication it brings. On the positive side, the M6 is quicker than the M5 saloon, and although it’s not as practical, it looks fantastic. There’s a growing demand for powerful, naturally aspirated engines, too.”

Buyer beware...

â–  Engine: Listen for valvetrain noise and grumbles from below, hopefully signalled by the engine warning light before terminal crank failure occurs. Check the service history for on-the-button oil changes, which conrod bearings, in particular, require. Inspect the throttle bodies and actuators. Expect a healthy engine to consume a litre of oil every 1000 miles.

â–  Transmission: Even a sensibly used clutch lasts only 50,000 miles. (Check for the red cog warning light on the dashboard.) Expect the gearbox to be clunky around town but to free up with speed. A good one should pick up smoothly from rest and reverse without drama, although juddering may be a (relatively inexpensive) clutch release bearing and guide bush on its way out. Updated SMG3 ’boxes from 2006 onwards are more reliable than earlier ones. Whining and clunks from the rear diff are a no-no. Check it for oil leaks, too.

â–  Suspension, steering and brakes: Juddering through the steering wheel may be worn control arms. Replacement dampers for the electronic damper control system are expensive (about £600 each). Check for worn pads and lipped discs. Beware aftermarket alloy wheels, which may be oversized and rubbing the arches. Check tyres are premium brands.

â–  Body and interior: Check for water in the headlights and also in the cabin, which it enters via blocked roof drains. Problems with the hard drive can cause the iController to freeze on the BMW opening page.

Also worth knowing

Don’t downplay the significance of any warning lights. The MOT comes down hard on those, including the engine warning light and any deemed to be safety related, including brakes, tyre pressure sensors, airbags and stability control. Repairs could bankrupt you.

How much to spend

£9000-£12,499: Mainly early, private-sale cars around 100,000 miles optimistically priced but some with good histories and valuable recent work, including a 2005 car with 87,000 miles, full service history and new clutch and flywheel for £10,750.

£12,500-£13,999: Mainly lower-mileage 2006-07 cars with good service histories but, again, mainly private-sale examples.

£14,000-£18,999: Tidier cars with faultless service histories and around 50,000 miles.

£19,000-£21,000: Some exceptional, late-plate coupés and convertibles but also some merely good cars at strong prices.