Dearest cars cost 37 times more to repair than cheapest But once the warranty expires a motorist can face substantial bills should the car go wrong. The Discovery 3 is not the only car which can leave its owners digging deep into their pockets. VW Toureg drivers had to find £428. According to the study nearly a quarter of owners of older Discoveries suffered suspension problems, which are frequently expensive to repair with the bill running into several hundred pounds. Suspension faults were the most common problem for cars three years or older, affecting five per cent of the total. But for some models suspension was a problem for around on in five cars. "This suggests that potholes and poorly maintained British roads could be taking a toll on some cars as they age," the report says. Around five per cent of cars more than three years old needed repairs to their air conditioning or battery. However it was engine and emission repairs which led to cars being off the road for longest, in some cases more than two days. Exhaust faults were a particular problem for the VW Touareg and Skoda, affecting 15 and 16 per cent of cars respectively. Other costly problems to repair included engine mountings, piston rings, valves and pumps. Even newer cars under three years old are not without problems, the study found. Despite cars being under warranty they still appeared to have a knack of developing faults which were not covered. Worst hit were owners of the Smart superminis who had to find an average of £143 to meet repair bills, followed by the Skodia Fabia Estate, where the cost was £112 a year. With cars becoming increasingly sophisticated, it was their electrical systems which gave their owners the most difficulty. But it was repairs of the fuel system which caused the most inconvenience with more than 40 per cent of owners not getting their car back on the same day. A Volkswagen spokesman said: "Without full details of the survey by Which? we are unable to comment fully on this. However we would urge any Touareg customers who have concerns to contact their nearest Volkswagen Retailer to discuss. A Land Rover spokesman said the results were not representative of its current range. The survey looks at a car that we no longer manufacture; the vehicles included are between four and nearly ten years old and do not represent the real progress that Land Rover has made recently in terms of cost of ownership and quality.