Used buyers opting for a diesel will have to do over 56k miles before they see the benefits of paying more for an oil-burner, according to an on-line used-car price guide. Wisebuyers.co.uk says that diesel price premiums and higher service costs mean the idea that diesels make economic sense could be a myth unless you’re doing mega-miles. Wisebuyer’s figures show that a 12-month old Ford Focus 1.8 TDCi LX costs £1150 more than the 1.6-litre petrol version. With current fuel prices the saving for the diesel is only 2.04p per mile – leaving you to do 56,373 miles before recouping the extra outlay for the TDCi. However, diesel cars generally have a higher resale value.