GMC Hummer H3 2008 Owner's Handbook Manual page 259

Service and Maintenance
NOTICE
Do not substitute any liquids for
the proper coolant mixture.
Otherwise, premature corro-
sion may result and the engine
coolant will require change
sooner.
Damage caused by the use of
any coolant that is not recom-
mended is not covered by your
new vehicle warranty.
. . . 258
Check the coolant level at regular
intervals, such as when refuelling.
The coolant level can be checked
by looking at the see-through
recovery reservoir without having
to remove the cap.
The vehicle must be on a level
surface.
The level should be at or above the
FULL COLD mark.
If the coolant level is low, add a
50/50 mixture of water and DEX-
®
COOL coolant to bring the level
to the proper mark.
Then replace the cap. Be sure the
cap is tight.