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Driving On Grades
Reduce speed and shift to a lower gearbeforestartingdown a long or steep downgrade. If the transmission isnot shifted down, the brakes might get hot and nolonger work well.
Vehicles can tow in D (Drive). Shift the transmission toa lower gear if the transmission shifts too often underheavy loads and/or hilly conditions.
The tow/haul mode may be used if the transmissionshifts too often. SeeTow/Haul Mode on page 3!36.
When towing at high altitude on steep uphill grades,consider the following: Engine coolant will boil at alower temperature than at normal altitudes. If the engineis turned off immediately after towing at high altitude onsteep uphill grades, the vehicle may show signs similarto engine overheating. To avoid this, let the engine runwhile parked, preferably on level ground, with theautomatic transmission in P (Park) for a few minutesbefore turning the engine off. If the overheat warningcomes on, seeEngine Overheating on page 7!34.
Parking on Hills
{WARNING:
Parking the vehicle on a hill with the trailer
attached can be dangerous. If something goes
wrong, the rig could start to move. People can be
injured, and both the vehicle and the trailer can be
damaged. When possible, always park the rig on
a flat surface.
If parking the rig on a hill:
1. Press the brake pedal, but do not shift intoP (Park) yet. Turn the wheels into the curb if facingdownhill or into traffic if facing uphill.
2. Have someone place chocks under the trailerwheels.
3. When the wheel chocks are in place, release theregular brakes until the chocks absorb the load.
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Page 465 of 616

What Kind of Engine Oil to Use
Look for three things:
.GM4718M
This vehicle's engine requires a special oil meetingGM Standard GM4718M. Oils meeting thisstandard may be identified as synthetic. However,not all synthetic oils will meet this GM standard.Use only an oil that meets GM StandardGM4718M.
Notice:Using oils that do not have the GM4718MStandard designation can cause engine damage notcovered by the vehicle warranty.
.SAE 5W-30
SAE 5W-30 is best for the vehicle. These numberson an oil container show its viscosity, or thickness.Do not use other viscosity oils such asSAE 20W-50.
.American Petroleum Institute (API) starburstsymbol
Oils meeting theserequirements should havethe starburst symbol onthe container. This symbolindicates that the oil hasbeen certified by theAmerican PetroleumInstitute (API).
This vehicle's engine was filled at the factory with aMobil 1®synthetic oil meeting all requirements for thisvehicle.
Substitute Engine Oil: When adding oil to maintainengine oil level, oil meeting GM Standard GM4718Mmight not be available. You can add substitute oildesignated SAE 5W-30 with the starburst symbol at alltemperatures. Substitute oil not meeting GM StandardGM4718M should not be used for an oil change.
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Page 466 of 616

Engine Oil Additives / Engine Oil
Flushes
Do not add anything to the oil. The recommended oilswith the starburst symbol that meet GM standards areall that is needed for good performance and engineprotection.
Engine oil system flushes are not recommended andcould cause engine damage not covered by the vehiclewarranty.
Engine Oil Life System
When to Change Engine Oil
This vehicle has a computer system that indicates whento change the engine oil and filter. This is based onengine revolutions and engine temperature, and not onmileage. Based on driving conditions, the mileage atwhich an oil change is indicated can vary considerably.For the oil life system to work properly, the system mustbe reset every time the oil is changed.
When the system has calculated that oil life has beendiminished, it indicates that an oil change is necessary.A CHANGE ENGINE OIL SOON message comes on.SeeDIC Warnings and Messageson page 4!48.Change the oil as soon as possible within the next600 miles (1 000 km). It is possible that, if driving underthe best conditions, the oil life system might not indicatethat an oil change is necessary for over a year.However, the engine oil and filter must be changed atleast once a year and at this time the system must bereset. Your dealer/retailer has trained service peoplewho will perform this work using genuine parts andreset the system. It is also important to check the oilregularly and keep it at the proper level.
If the system is ever reset accidentally, the oil must bechanged at 3,000 miles (5 000 km) since the last oilchange. Remember to reset the oil life systemwhenever the oil is changed.
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Page 476 of 616

What to Use
{WARNING:
Adding only plain water to the cooling system can
be dangerous. Plain water, or some other liquid
such as alcohol, can boil before the proper
coolant mixture will. The vehicle's coolant warning
system is set for the proper coolant mixture. With
plain water or the wrong mixture, the engine could
get too hot but you would not get the overheat
warning. The engine could catch fire and you or
others could be burned. Use a 50/50 mixture of
clean, drinkable water and DEX-COOL®coolant.
Use a 50/50 mixture of clean, drinkable water andDEX-COOL®coolant. If using this mixture, nothingelse needs to be added. This mixture:
.Gives freezing protection down to!34°F (!37°C),outside temperature.
.Gives boiling protection up to 265°F (129°C),engine temperature.
.Protects against rust and corrosion.
.Will not damage aluminum parts.
.Helps keep the proper engine temperature.
Notice:If an improper coolant mixture is used, theengine could overheat and be badly damaged. Therepair cost would not be covered by the vehiclewarranty. Too much water in the mixture can freezeand crack the engine, radiator, heater core, andother parts.
Notice:If extra inhibitors and/or additives are usedin the vehicle's cooling system, the vehicle could bedamaged. Use only the proper mixture of the enginecoolant listed in this manual for the cooling system.SeeRecommended Fluids and Lubricantsonpage 8!10for more information.
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Page 483 of 616

Overheated Engine Protection
Operating Mode
If an overheated engine condition exists and theENGINE POWER IS REDUCED message is displayed,an overheat protection mode which alternates firinggroups of cylinders helps prevent engine damage. Inthis mode, you will notice a loss in power and engineperformance. This operating mode allows the vehicle tobe driven to a safe place in an emergency. Drivingextended miles (km) and/or towing a trailer in theoverheat protection mode should be avoided.
Notice:After driving in the overheated engineprotection operating mode, to avoid engine damage,allow the engine to cool before attempting anyrepair. The engine oil will be severely degraded.Repair the cause of coolant loss, change the oil andreset the oil life system. SeeEngine Oilonpage 7!17.
Engine Fan Noise
The vehicle has electric cooling fans. You might hearthe fans spinning at low speed during most everydaydriving. The fans can turn off if no cooling is required.Under heavy vehicle loading, trailer towing, and/or highoutside temperatures, or if you are operating the airconditioning system, the fans can change to high speedand you might hear an increase in fan noise. This isnormal and indicates that the cooling system isfunctioning properly. The fans change to low speedwhen additional cooling is no longer required.
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