GMC 2006 Sierra - Manual (Page 421)

To ensure quick starts in the wintertime, the E85 fuel
must be formulated properly for your climate according to
ASTM specification D 5798. If you have trouble starting
on E85, it may be because your E85 fuel is not properly
formulated for your climate. If this happens, switching to
gasoline or adding gasoline to your fuel tank may improve
starting. Your vehicle is designed to accommodate a
mixture of gasoline and E85 fuel. For good starting and
heater efficiency below 32°F (0°C), the fuel mix in the fuel
tank should contain no more than 70% ethanol.
E85 has less energy per gallon than gasoline, so you will
need to refill your fuel tank more often when using E85
than when you are using gasoline. Regular unleaded
gasoline is recommended when pulling a trailer. For
payload capacity with ethanol fuel, see Loading Your
Vehicle on page 4-48.
Notice: Some additives are not compatible with E85
fuel and may harm your fuel system. Damage caused
by additives would not be covered by your new
vehicle warranty. Do not use additives with E85 fuel.
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.
Fuels in Foreign Countries
If you plan on driving in another country outside the
United States or Canada, the proper fuel may 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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