Petrol v's Diesel v's LPG

Although there are a wide variety of fuels and emerging technologies, there are only three main fuels that are currently widely available enough to cater for all driving situations: Petrol, Diesel and LPG (Liquid Propane Gas).
There is no clear argument in favour of any of these three fuels, as each has its own particular advantages and disadvantages.

LPG has lower CO and CO2 emissions than petrol, but higher NOx emissions. In comparison with diesel, LPG has lower emissions of NOx and particulates but higher emissions of CO and HC. LPG is cheaper than petrol and diesel due to reduced levels of taxation, and fuel costs are typically around 40% less than petrol or diesel cars. However they require an additional fuel tank which can increase the weight of the car and decrease the fuel-efficiency and take up boot space. The conversion cost is around £1,000-2,000. Converted vehicles retain the ability to run on petrol if they are unable to refill with LPG. The government Powershift grant to assist with conversion costs to LPG is no longer available, which means that the added cost of conversion off-sets some of the reduced running costs.
So which is the right choice? Only you can answer that. If you’re reading this you then you are obviously keen to reduce your environmental motoring impact. So make a short list of different cars with different fuels to test drive. Then pick the car that has the lowest emissions, is the best overall deal and the one you liked driving the most. That way you’ll save money, the environment and the agony of having a car you detest.
The Department of Health (COMEAP, 1999) guidance states that ‘...definitive advice as to the preferability, on health grounds, of diesel vs petrol-powered light vehicles is not possible. However, concerns about the effects of particles on health in urban areas currently tip the balance in favour of petrol’. Also, Friends of the Earth does not recommend diesel for cars that are predominantly used for driving in towns.