California Fuel; Additives - GMC 2004 Yokon Denali Owner's Manual

California Fuel

If your vehicle is certified to meet California Emission
Standards (see the underhood emission control
label), it is designed to operate on fuels that meet
California specifications. If this fuel is not available in
states adopting California emissions standards,
your vehicle will operate satisfactorily on fuels meeting
federal specifications, but emission control system
performance may be affected. The malfunction indicator
lamp may turn on (see Malfunction Indicator Lamp
on page 3-42 ) and your vehicle may fail a smog-check
test. If this occurs, return to your authorized GM
dealer for diagnosis. If it is determined that the condition
is caused by the type of fuel used, repairs may not be
covered by your warranty.
5-6

Additives

To provide cleaner air, all gasolines in the United States
are now required to contain additives that will help
prevent engine and fuel system deposits from forming,
allowing your emission control system to work
properly. You should not have to add anything to your
fuel. However, some gasolines contain only the
minimum amount of additive required to meet
U.S. Environmental Protection Agency regulations.
General Motors recommends that you buy gasolines that
are advertised to help keep fuel injectors and intake
valves clean. If your vehicle experiences problems due
to dirty injectors or valves, try a different brand of
gasoline.
Gasolines containing oxygenates, such as ethers and
ethanol, and reformulated gasolines may be available in
your area to contribute to clean air. General Motors
recommends that you use these gasolines, particularly if
they comply with the specifications described earlier.