GMC 2009 Sierra - Manual (Page 319)

Notice: Your vehicle was not designed for fuel
that contains methanol. Do not use fuel containing
methanol. It can corrode metal parts in the fuel
system and also damage plastic and rubber parts.
That damage would not be covered under your
warranty.
Some gasolines that are not reformulated for low
emissions can contain an octane-enhancing additive
called methylcyclopentadienyl manganese tricarbonyl
(MMT); ask the attendant where you buy gasoline
whether the fuel contains MMT. We recommend
against the use of such gasolines. Fuels containing
MMT can reduce the life of spark plugs and the
performance of the emission control system could be
affected. The malfunction indicator lamp might turn on.
If this occurs, return to your dealer/retailer for service.
Fuels in Foreign Countries
If you plan on driving in another country outside the
United States or Canada, the proper fuel might be
hard to find. Never use leaded gasoline or any other
fuel not recommended in the previous text on fuel.
Costly repairs caused by use of improper fuel would
not be covered by your warranty.
To check the fuel availability, ask an auto club,
or contact a major oil company that does business
in the country where you will be driving.
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