An experimental study was conducted on in-use and new, Indian two-wheelers to study the effect of gasoline composition (olefins, aromatics and benzene) on exhaust mass emissions. Exhaust emissions of benzene were also measured. The study was conducted on six makes of new and in-use, two-wheelers consisting of popular 2-stroke and 4-stroke, mopeds, scooters and motorcycles. Three test fuels, a high olefin gasoline, a high aromatic gasoline and a Euro-III equivalent gasoline were used for the study. High olefin test gasoline contained 26.5% olefins, 10.3% aromatics and 0.3% benzene. High aromatic test gasoline contained 0.9% olefins, 61.9% aromatics and 1.5% benzene. Euro-III test gasoline contained 15.9% olefins, 37.4% aromatics and 0.9% benzene. Intake system deposit study was also conducted on 4-stroke motorcycles and two-stroke scooters having separate lubrication, using two fuels, i.e. high olefin gasoline and Euro-III gasoline, with and without the use of multi-function additives.
Studies show that isolating the effect of an individual compositional characteristic may be difficult. Higher benzene content in the fuel led to higher benzene in the exhaust. High olefin gasoline resulted in higher CO and lower NOx emissions compared to high aromatic gasoline. The emissions from in-use vehicles were higher than new vehicles. It was seen that the benzene emissions from in-use, 2-stroke vehicles were very high compared to new 2-stroke vehicles. This was mainly because of the in-use, 2-stroke vehicles having no catalytic converter. The study showed that lowering the benzene content in the fuel would greatly help to reduce exhaust benzene emissions. Multi-functional additives were seen to be very effective to control intake system deposits.