The wine comes from an English vineyard in Wiltshire, and the EU limits how much wine a vineyard can produce, so the vineyard sells the overage to Green Fuels, which turns it into biofuels and supplies it to the Palace.
The Aston can go ten miles on a gallon of gas, which would equate to 45 bottles of wine to go the same distance. The wine, though, puts out 85-percent less CO2 and costs £1.10 per liter, which is slightly less than the cost of gas. However, Charles only goes 300 miles in the car every year, and it's not like he's worried about gas prices, so the car won't make a difference by itself -- but he's got his royal heart in the right place.
[Source: Daily Mail]