LPG produces 33% less CO2 emissions than petrol and 45% less CO2 than diesel. LPG vehicles produce upto 82% less Nitrogen Oxide pollutants than petrol and 99% better than diesel !
63% less Carbon Monoxide.
40% less Hydrocarbons than petrol and 70% less than diesel.
50% less particulates than petrol and 98% less than diesel. These caused the London warning in 2005.