hello!
yaar its a fact that every thing here has just taken as dangerous or some thing horrible like we all take CNG....incorrect usage and incorrect setting might make CNG a worst thing for ur car...but using it properly can make u run ur car not smoother but saving ur lot of money..
As u ask that how CNG can affect ur engine life and how its harms engine..so
CNG(methane) burns hot...so it can effect valve seats....just due to its nature....
It is difficult to pass spark out of CNG(Methane)..so it requires much stronger spark than petrol.....also reduces plugs and ignition coil life...
need early replacement than petrol...
CNG as compared to petrol creates less power...an efficient settled car can create 85% of that power as produced by petrol....
Due to lack of power and burning hotter than gasoline...it requires some additional features in Lubrication oil...so engine oil is preffered as CNG oil and can be replaced after every 4500 -5000Km for normal engine life....
if ur engine is weak a bit and install CNG..so due to all of these features..rings and other stuff just wear out earlier...
so be careful before installing CNG...engine rings must be in perfect condition....or it can drink oil and losses power and milage also...
so these are the facts and figure behind this....if properly installed and main thing is tuning...if u ge proper tuning and installation..and a strong healthy engine..no doubtu can run ur car on CNG....just need a little care....
Thanxxx