http://www.go-lpg.co.uk/BMWV12.html

I'm running an E34-535i on LPG since 1.5 years. Infrastructure is almost exploding with current gas prices and waiting time for having a kit installed is currently roughly 4 months. Not even a new technology, less than have the cost of normal fuel (Euro0,64/liter vs. Euro 1,55/liter for gasoline) and meanwhile easily available. More & more people in Germany are converting their cars and I don't understand why none of the big car makers offer it as a factory option (only SUBARU does to my knowledge).