I'm just wondering *why* diesel is higher than unleaded, without searching I seem to recall that it is actually easier to produce diesel than petrol as it needs less refinement ?
In which case it should be a fraction less in cost.
I suppose the explosion in popularity of derv powered cars in the early to mid 90's helped a lot, although I do remember when a bit younger fuel was around 39 or 40 pence per litre back then you could still get 'real' leaded fuel too
I do not recall the price of derv although I'm sure it used to be generally a fair bit (not just 2 or 3 pence) cheaper than petrol... Around 5 to 10 pence I seem to think although that may well be my imagination.
EDIT... Tidied topic slightly.