Fuel: leaded vs unleaded

[Martin K.]

Australia

I have heard conflicting reports about the use of unleaded fuels in vehicles not equiped with catalytic converters, my preference is to use a locally available high octane (98) unleaded fuel. I have been told that benzene emissions are high as there is no converter to clean up the combustion gasses. Others have said that the benzene emissions are no higher than the old leaded fuel.
Apart from benzene are there any other emission nastys associated with using unleaded in a pre catalytic vehicle.

[Duke W.]

Re: Fuel: leaded vs unleaded

Modern unleaded fuels generally have fewer "aromatics" (which includes benzene) than the leaded fuels of yore. Aromatics have high octane, but they also have high vapor pressure, which is primarily why they are limited as blending consituents for modern fuels.

Don't get hung up on emissions. It's a VERY complicated issue, and there are a lot of oversimplifications and myths floating around. Find a proper fuel or blend of fuels that allows your car to operate without detonation, and don't worry about emissions.

Duke