poor civic will go through a hard time and u will be saying 'why did i installed cng'!. bro dont install cng. it will ruin your car. your suspension will also be affected. well my civic VTi 2005 manual has done 4000km in two years, which is very low. it gives me 10km/litre in city WITH ac, on highway WITH ac it does almost 12-13km/litre. never gonna install cng in ma car. its up to u.