GMC 2006 Sierra - Manual (Page 420)

Gasolines containing oxygenates, such as ethers and
ethanol, and reformulated gasolines may be available
in your area. General Motors recommends that you use
these gasolines if they comply with the specifications
described earlier. However, E85 (85% ethanol) and other
fuels containing more than 10% ethanol must not be
used in vehicles that were not designed for those fuels.
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
recommends against 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.
Fuel E85 (85% Ethanol)
The 8th digit of your vehicle identification number (VIN)
shows the code letter or number that identifies your
engine. You will find the VIN at the top left of the
instrument panel. See Vehicle Identification
Number (VIN) on page 5-122.
If your vehicle has the 5.3L V8 engine (VIN Code Z only),
you may use either regular unleaded gasoline or ethanol
fuel containing up to 85% ethanol (E85); also see Fuel on
page 5-5. In all other engines, including the 5.3L V8 (VIN
Code T), use only regular unleaded gasoline.
Only vehicles that have the 5.3L V8 engine (VIN Code Z)
may use 85% ethanol fuel (E85). General Motors
encourages the use of E85 in vehicles that are designed
to use it. The ethanol in E85 is a “renewable” fuel,
meaning it is made from renewable sources such as
corn and other crops.
Many service stations will not have an 85% ethanol
fuel (E85) pump available. The U. S. Department
of Energy has an alternative fuels website
(http://www.eere.energy.gov/afdc/infrastructure/
locator.html) that can help you find E85 fuel. Those
stations that do have E85 should have a label indicating
ethanol content. Do not use the fuel if the ethanol content
is greater than 85%.
At a minimum, E85 should meet ASTM Specification
D 5798.
5-8