Adding Equipment To The Outside Of The Vehicle; Fuel; Gasoline Octane; Gasoline Specifications - Hummer H2 2009 Owner's Manual

Keep a record with all parts receipts and list the
mileage and the date of any service work performed.
See Maintenance Record on page 6-17.
Adding Equipment to the Outside of
the Vehicle
Things added to the outside of the vehicle can affect the
airflow around it. This can cause wind noise and can
affect fuel economy and windshield washer performance.
Check with your dealer/retailer before adding equipment
to the outside of the vehicle.

Fuel

Use of the recommended fuel is an important part of
the proper maintenance of this vehicle. To help keep the
engine clean and maintain optimum vehicle performance,
we recommend the use of gasoline advertised as
TOP TIER Detergent Gasoline.
This vehicle can use either unleaded gasoline or
ethanol fuel containing up to 85% ethanol (E85).
See Gasoline Octane on page 5-5 and
Fuel E85 (85% Ethanol) on page 5-7.

Gasoline Octane

Use premium unleaded gasoline with a posted octane
rating of 91 or higher. You can also use regular unleaded
gasoline rated at 87 octane or higher, but the vehicle's
acceleration could be slightly reduced, and you might
notice a slight audible knocking noise, commonly referred
to as spark knock. If the octane is less than 87, you might
notice a heavy knocking noise when you drive. If this
occurs, use a gasoline rated at 87 octane or higher as
soon as possible. Otherwise, you could damage the
engine. If you are using gasoline rated at 87 octane or
higher and you hear heavy knocking, the engine needs
service.
Gasoline Specifications
At a minimum, gasoline should meet ASTM specification
D 4814 in the United States or CAN/CGSB-3.5 or 3.511
in Canada. Some gasolines contain an octane-enhancing
additive called methylcyclopentadienyl manganese
tricarbonyl (MMT). We recommend against the use of
gasolines containing MMT. See Additives on page 5-6 for
additional information.
5-5