Glass's Market Intelligence Service has looked at the wholelife costs of a range of diesel cars from volume to premium sector to produce the findings.
The analysis covered every aspect of the total cost of ownership, for six upper-medium diesel models over a three-year/60,000 mile period.
The selected cars, which have a comparable specification and power output, were the Audi A4 1.9 TDi SE saloon, BMW 320d saloon, Ford Mondeo 2.0 TDCi 130 Ghia hatchback, Mercedes-Benz C200 CDI Classic saloon, Renault Laguna 2.2 dCi Privilege hatchback, and Vauxhall Vectra 2.0 DTi Elite hatchback.
The research took into account the original purchase price, including the discount that a typical buyer might be expected to secure, depreciation after three years/ 60,000 miles, maintenance and repair costs, the cost of replacing five tyres, road tax, insurance, interest on the capital (at 4%) and fuel consumption (using manufacturers' data).
Based on an analysis of this information, the BMW 320d has the lowest wholelife cost, followed very closely by the Ford Mondeo TDCi.
The BMW's position comes as a direct result of the free servicing package currently offered with the car – without it the Ford would be placed first.
Ranked third and fourth are the Audi A4 TDi SE and the Renault Laguna 2.2dCi Privilege. Out of the six vehicles assessed, the most expensive models to own and run would be the Mercedes C200 CDI Classic in fifth place, and the Vectra 2.0 DTi Elite placed last.
Alan Cole, consultant for Glass's Market Intelligence Service, said: 'Particularly interesting is the fact that the difference in cost between the best and the worst performer is a mere £789 over the three years and 60,000 miles.
'Depreciation remains one of the biggest factors influencing overall whole life costs, but buyers must always balance the strong residual values of prestige-brand cars against the higher purchase price and greater insurance costs.'