There is this wonderful thing called an owners manual. It lists such items as oil capacity
6 qts. for both the 3.7 and 5.3 liter engines.
5 quarts (with an oil filter change)
It takes 6 quarts of 5w30
3.5 quarts
6 quarts synthetic 5W-30 Filter is an AC Delco PF46, FRAM PH3506, etc
6.4 quarts of engine oil with filter change.
7 quarts.
You will need to drop the oil pan to change the oil pan on a Hummer 2. The oil pan is located in inside the oil pan. You also need to first drain the oil pan of the old oil before you drop the pan.
If you have the new V-6 engine, (non compressor engine) then the capacity is 8.5 qts. with oil filter change.
6 qts with filter change.
6.5 quarts with filter change.