325i N52 / N53

The N52 is the reason people still recommend this generation. It's smooth to 7,000 rpm, has no high-pressure fuel system, no turbos and no carbon service, and it doesn't have a single failure mode that writes off the car. Yet what it does have is a set of hardened gaskets and a plastic-and-electronics cooling system that's now old. Budget €1,000–1,500 in the first year to bring the cooling and the oil leaks up to date, then it's one of the cheapest six-cylinder BMWs to keep on the road. Manual cars are worth seeking out; the six-speed automatic is fine but blunts it.

This is the quiet trap of the range. On the face of it you're buying the sensible naturally aspirated six, with no turbos and the same durable block underneath, and mechanically that's exactly what it is. But the lean-burn direct injection brought piezo injectors and NOx sensors with it, and both are wear items that add up to four figures. Sellers rarely raise any of this, because the car drives perfectly normally right up until an injector goes. So ask for injector receipts and their index numbers, then scan for per-cylinder misfires. Done properly, this is a good car with a decade left in it. Bought blind, it is the reason people say they will never buy another BMW.