BMW M5 and Audi RS4: TG mag's guide to used hero cars

In this month's issue of Top Gear magazine, Chris Harris is your guide to navigating through the world of secondhand superheroes. That's right - he's picked some of the finest used car metal you can purchase. You're welcome. “There is nothing I would rather do than make a decent cup of builders’ tea and settle down to a good long session of internet dreaming,” Harris explains.

Two of these are that most heroic of BMW M cars, the E39 M5, and the V8-powered B7 Audi RS4.

BMW M5 (E39): £10,000-£40,000

This is a brilliantly simple car. Beefy 5.0-litre 394bhp V8, six-speed manual gearbox, rudimentary traction control, a sport button that did no more than sharpen throttle response, some seats, a decent boot, subtly enhanced bodywork and... that's it. There's a purity and elegance to the E39 M5 that guarantees its status as a future great.

However, the Vanos valve-timing system was always noisy at start-up. If it doesn't quieten down once warm, then it will need attention. Like the RS4, the engine can also suffer from a build-up of oil residue that hardens into a carbon deposit in the cylinder heads. Here it's less likely to do damage, and it's worth knowing the Vanos system can be refurbed.

Porous rear diff seals will be expensive to sort, and rust can rear its ugly head. As ever, it's the sills and arches to look at first. Assuming you get a car you're happy with, we'd advise you to find a good indepedent specialist, as parts and labour will be much more cost-effective than in the main dealer network - and knowledge of older cars is likely to be better, too. Properly maintained, this is a big-hearted, laid-back, yet crisp muscle saloon.

+ 5.0-litre V8, manual gearbox. Pure. Simple
- Valve timing a bit brittle

Audi RS4 (B7): £13,000-£30,000

The B7, that's the RS4 to have. It featured Dynamic Ride Control, a mechanical system that diagonally cross-linked the dampers, making the RS4 both poised and supple. Here was a sports saloon (and estate) that rode well. It was a trend that Audi soon abandoned. And then there was the high-compression 12.5:1 naturally aspirated 4.2-litre V8. These days it doesn't feel desperately fast or loud, but there's a woofly sophistication to the whole car.

It was never efficient, though. Expect 18mpg, and the 326g/km CO2 figure means that your annual tax bill will be £535. There are issues to watch out for as well. The DRC system can leak, the switchable exhaust valves can seize, and although the engine is tough, cars that have had a life of start/stop urban driving will probably have built up carbon deposits on the inlet valves which will need professional attention. If the engine doesn't run smoothly, best walk away.

These are highly regarded cars, and values are increasing. Maybe enough to outweigh the running costs. Pristine low-mileage cars can command £30k, but half that is enough to get you a decent runner.

+ Woofly n/a engine a dying species
- Quick! Prices are rising

There's much more excellent used car buying advice in this month's TG mag, from sports cars to more fast executives, and hot hatches to Japanese heroes. Plus, we drive Colin McRae's old WRC Impreza around Tokyo, go on a Chilean adventure in Merc's X-Class pick-up, take an Ariel Nomad up a mountain, and more.

It's your last chance to pick up a copy now, so make haste! There are links below, or you can go and walk to your local newsagents, where there are also crisps and sweets available.

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