[Gibbo]

I first owned a Diesel car 5 years ago and the cost difference per litre was 2p or about 10p a gallon. Now the difference is 10p a litre or nearly 50p a gallon. At a base commodity level I can only assume this is supply and demand based and if so will this price gap widen in the future or even off?

If it widens further my thoughts lead to what effect this will have on the car market and specifically the everyday performance car. For example, VW are moving towards more powerful smaller efficient engines with the 1.4 turbo/supercharged engine with upto 170bhp. This engine has a claimed average of 38mpg. Also the 1.6 170bhp unit in the mini has an average of 45mpg. Plus there is the efficient BMW 4 cylinder engines.

So in the near future if we can have claimed 40mpg engines (I know they will do a bit less in the real world) how will these compare to diesels.

At 40mpg - diesel 10% premium has to do 44mpg equivalent
At 40mpg - diesel 20% premium has to do 48mpg equivalent

On top of this the cost of a diesel car is normally atleast £1,000 more than the equivalent petrol and it makes a very strong case for itself unless you are a very high mileage driver.