The energy density of oil

"When you draw 10 gallons [45.46L] of fuel into the tank of your car, in the sixty seconds it takes the energy flow is equivalent to the full output of a 25 megawatt power station."

- James Lovelock, The Vanishing Face of Gaia:
A Final Warning (London: Penguin, 2009), 64.

We have never found a substance as useful and powerful as oil. It is the distilled power of thousands of years of ancient sunlight poured into your petrol tank. Of course, oil is indeed a natural and renewable resource. It is just that the oil we use globally each year takes about three million years for the earth to replenish.*

Happy driving.
*This claim comes from How Earth Made Us, a fascinating BBC documentary series hosted by Prof Iain Stewart (and available on iPlayer to UK residents if you are very quick). I've also just read (amongst other things) this article in New Scientist, which gives a useful update on the state of "non-conventional" sources of oil. These include Canada's tar sands and large amounts of oil shale in the US. Bottom line: there are truly huge source of unconventional oil still in the ground, but getting them out will be very tricky. At the moment, they still do not represent a silver bullet for an impending energy shortfall.