the answer that "We are still supplyng oil bought when the price was high" is in part BS. Prices at the pump adjust quickly to crude pricing as the basis of pricing is what is termed as "current pricing" or LIFO in accountancy, Last In First Out.
Failure to practice this could risk serious discords and even major cash-flow issues (insolvency) if a company (and not just oil but anything) prices to historic or a FIFO basis.
In practice there may be a lag effect as supply contracts are built like club sandwiches of term prices but there is always an element of todays (spot) market in the pricing, called Platts, but this is merely the execution of accounting and nothing to do with the rationale of pricing at the pump.
Platts has been fairly constant this month with a slight rise, reflecting concerns on Libya.
see
http://www.oil-price.net/
Libya is indeed small beer in world terms and Saudi has indicated it would cover the supply deficit with their light oil. Libyan crude is fantastic crude as it is very light and "sweet" (without sulphur). A good percentage of their exports (circa 1.4 million barrels a day) has ended up in the UK, mainly running through Shell's Stanlow refinery near Chester. It is a great crude to make petrol and diesels from......
L