Additives - Hummer H2 2004 Owner's Manual

The malfunction indicator lamp may turn on (see
Malfunction Indicator Lamp on page 3-37 ) 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.

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.
5-6
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.
Notice: Your vehicle was not designed for fuel that
contains methanol. Do not use fuel containing
methanol. It can corrode metal parts in your fuel
system and also damage the plastic and rubber
parts. That damage would not be covered under
your warranty.
Some gasolines that are not reformulated for low
emissions may contain an octane-enhancing additive
called methylcyclopentadienyl manganese
tricarbonyl (MMT); ask the attendant where you buy
gasoline whether the fuel contains MMT. General Motors
does not recommend the use of such gasolines.
Fuels containing MMT can reduce the life of spark plugs
and the performance of the emission control system
may be affected. The malfunction indicator lamp
may turn on. If this occurs, return to your authorized GM
dealer for service.