Gasoline and diesel fuel prices are high in many countries.
For instance, in Turkey, the 97-octane gasoline is 2.45 US dollar per liter. The Euro-Diesel fuel is 2.23 US dollar per liter. 1 liter LPG is 1.53 in US dollar. (4 liters equal ~1 gallon)
In Turkey, 42% of cars use LPG (Liquefied petroleum gas). The 32% of cars use only gasoline and the 26% of cars use only diesel fuel.
There is a growing interest for the use of LPG. In addition, it is environmentally friendly, it does not reduce the performance of a car and I believe LPG is safe for using in gasoline-powered car engines.