Page 213 of 366

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.
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.
5-7
Page 308 of 366
Part Engine
(RPO Code)GM Part
NumberACDelco®Part
NumberOther Part
Numbers
Pressure Caps
6.6L (LB7/LLY)
7.2L (LG5)
7.8L (LG4)
8.1L (L18)15075118
—
15075118
15997145—
—
—
——
—
—
—
Secondary Fuel Filter
6.6L (LB7/LLY)
7.2L (LG5)
7.8L (LG4)
8.1L (L18)—
—
15098649
25055052—
—
—
——
CAT 1R0751
—
—
Spark Plugs
6.6L (LB7/LLY)
7.2L (LG5)
7.8L (LG4)
8.1L (L18)—
—
—
——
—
—
41-983—
—
—
—
*Optional Davco (K28) D350921 spin-on type filter located on driver’s side frame rail.
**Optional Cold Weather (KUK) Racor B6484GM spin-on type filter located on driver’s side frame rail.
***Optional air filter (GM Part No. 88937525) for C6/C7/C8 Models. Fits inside standard size filter (GM Part No.
88937548) listed previously.
5-102
Page 332 of 366

(24)= Check the air intake system installation to see
that gaskets are seated properly and all hose
connections, fasteners and other components are tight.
Tighten connections and fasteners or replace parts
as required.
(26)= Evaporative Control System Service (if equipped):
Check all fuel and vapor lines and hoses for proper
connections and correct routing (or every 24 months,
whichever occurs first). Replace parts as needed.
(28)= Replace spark plugs. Inspect wires for damage.
Check the wire boot and boot heat shield fit at spark
plugs and coil. Replace parts as needed.
(30)= Check the fuel tank, fuel cap and fuel lines for
damage which could cause leakage. Inspect fuel cap for
correct sealing ability and any indications of damage.
Check fuel cap gasket for even filler neck imprint.
Replace parts as needed.
(31)= Check EGR system as described in the service
manual. SeeService Publications Ordering Information
on page 7-7.(32)= Inspect Electronic Vacuum Regulator Valve
(EVRV) filter for excessive contamination or plugging. If
needed, clean filter with solution of soap and water,
let dry and install.
(35)= Drain, flush and refill cooling system. SeePart C:
Recommended Fluids and Lubricants on page 6-29
for what to use. Inspect hoses. Clean radiator,
condenser, pressure cap and neck. Pressure test
cooling system and pressure cap. For Caterpillar
®diesel
engines, always refer to the Caterpillar®Diesel Engine
Operation & Maintenance Manual for coolant
recommendations and change intervals.
(37)= Rear axle service: Change the lubricant. See
Part C: Recommended Fluids and Lubricants on
page 6-29.
(38)= Front axle service: Re-pack upper kingpin roller
bearing.
6-22