I'll say it one more time for those of you that missed it. Check your owners manual and follow the directions to the letter. The GM car I usually refer to is a Northstar Cadillac, ANY Northstar Cadillac. This one happens to be a '99 STS. They are designed to use dino oil, not synthetic, they are designed to give extremely rapid oil draindown, and they are designed to have the oil level checked when HOT. This engine holds 7.5 quarts of oil in the crankcase, but will be perfectly fine running with 5, it just won't pull 1G in a corner for very long without starving for oil. Since I usually don't drive my car that way, it is OK for me to keep my oil level at 7 quarts. This puts it RIGHT ABOVE THE ADD MARK when cold and after sitting in a garage overnight. The result? 29 MPG at 74 average MPH on a 2000 mile trip, using about 6 ounces of oil total. Specific to this type and design engine? Maybe, not many engines will even hold 7.5 quarts of oil. Can you argue with the instructions in the owners manual? I Don't Think So. Should you keep the oil level at the "FULL" mark on this engine, even when cold? NO!!!