If you are considering converting your car into LPG... consider the following comparison chart.
LPG for transport
LPG is a liquid that is a by product from the refinery processing oil. The reason for virtually no one is running on this fuel in Denmark today is that tax rules were changed in the 1980s. But there are still a few stations back offering LPG gas and in Norway there are approximately 25,000 cars that have LPG as a propellant.
Benefits of LPG cars are that ordinary cars relatively easily are rebuilt to run on LPG gas and there are conversion kits for ordinary gasoline cars.
LPG gas is not stored under high pressure, but only need an operating pressure of 10 bar which is very little compared the operating pressure of natural gas at 200 bar. The low pressure makes it easier to build tanks.
LPG vehicles have CO2 emissions levels like ordinary petrol cars and higher particulate emissions than natural gas, so there are no environmental benefit. Another problem is the explosion hazard, which is quite big.
Denmark has earlier had many buses running on LPG gas, but they are also moving away.