8.8 Can I used unleaded on older vehicles?
Description
This article is from the Gasoline FAQ, by Bruce Hamilton with numerous contributions by others.
8.8 Can I used unleaded on older vehicles?
Yes, providing the octane is appropriate. There are some older engines that
cut the valve seats directly into the cylinder head ( eg BMC minis ). The
absence of lead, which lubricated the valve seat, causes the very hard
oxidation products of the exhaust valve to wear down the seat. This valve
seat recession is usually corrected by installing seat inserts, hardening
the seats, or use of specific valve seat recession protection additives
( such as Valvemaster ). Most other problems arise because the fuels have
different volatility, or the reduction of combustion chamber deposits.
These can usually be cured by reference to the vehicle manufacturer, who
will probably have a publication with the changes. Some vehicles will
perform as well on unleaded with a slightly lower octane than recommended
leaded fuel, due to the significant reduction in deposits from modern
unleaded gasolines. If premium unleaded petrol containing relatively
high levels of aromatics is used, some carburetted engines from the 1960s
may experience spark plug fouling, however most vehicle manufacturers
have guides to ensure careful engine tuning will eliminate most of the
problem.
Continue to:
My Books
