#### LEAD CONTENT

Older, higher-compression engines usually required a gasoline with a higher octane rating. The most efficient way of increasing the octane rating of a gasoline was to add a compound called tetraethyl lead. Should circumstances force you to use a low-lead or no-lead gasoline with lower octane than the vehicle manufacturer specifies in an older lead fuel vehicle, you should temporarily retard the ignition timing very slightly in order to lessen the possibility of knocking. Some vehicles, though designed to operate on leaded gasoline, may be able to use low-lead and no-lead fuels. Again, experimentation is helpful in determining the gasoline octane that your vehicle and your driving require.