A false economy

I've always been interested in diesels, performance diesels, economical diesels and just the black stuff in general. Car journos are forever going on about the fact that used, pound for pound, petrol is better value. This runs counter to the prevailing thinking, and especially car marketing. Plenty of recent VW adverts promoted the fact that you'll fuel up once in a blue moon running on derv. Sales of motors powered by the clackety stuff are rocketing correspondingly. So a prestige used advert in todays InGear supplement of the Sunday Times caught my eye. Arnold Clark had two '03 plate Mercedes ML's side by side (not a car I particularly rate - but bear with me). Both metallic and both full leather. No mileage or condition was mentioned, so for the sake of argument we'll assume it's much of a muchness. The 270CDI diesel was £21k and the 500 V8 petrol £16k. Torque is about the same, however the diesel is just 200bhp whilst the V8 is 300bhp. Driving conservatively you'll be doing well to get 30 mpg from the diesel and 20 mpg from the petrol. Put a decent stainless steel exhaust on the V8 and it'll sound like a muscle car. The diesel on the other hand will always have more in common with one of Kelvin Kabs finest. If you do 10k per annum, then it's going to take you nigh on 7 years before the diesel starts saving you money over the petrol (assuming a couple of pence price differential per litre). I'll do a wee comparison on 3 litre Beemers tomorrow if I get a chance, and I suspect the same to be repeated. I know what I'll be getting next...