Pontiac 2002 Grand Prix Owner's Manual page 276

Turn off the engine and give the oil several minutes to
drain back into the oil pan. If you don't, the oil dipstick
might not show the actual level.
Pull out the dipstick and clean it with a paper towel or
cloth, then push it back in all the way. Remove it again,
keeping the tip down, and check the level.
3800 V6 Engine or 3800 V6 Supercharged Engine
3100 V6 Engine
6-14