I HAVE noticed that the price differential between diesel and petrol has now increased to 8p per litre.

Whereas I understand that fuel prices vary due to world crude oil availability and demand, the premium charged for diesel cannot be justified.

Historically, the duty (fuel tax) for diesel has been higher than petrol but this is now no longer the case.

The cost to refine diesel is less than petrol and the duty is now the same for both, at 60.97p per litre.

Excluding duty (to enable a fair comparison), diesel was 4p (- five per cent) cheaper than petrol in 2001, 1p (+ one per cent) more in 2006 and is currently in excess of 8p (+ six per cent) more expensive.

It is apparent that the oil companies are taking unfair advantage with a pricing structure which cannot be justified and are simply exploiting owner-drivers and companies who have invested in more expensive but energy-efficient diesel cars.

DAVID EYTON Lonsdale Road Summertown, Oxford