My 1996 Cadillac De Ville seems to be burning oil, no sign of a leak. Trying 16oz of MMO in oil to replace some it used. Will it help to put some in the gasoline as well? I’ve read some of these Northstar 4.6L engines tend to burn oil due to oil ring design.

One of the unique properties of Marvel Mystery Oil is that it can be used in both the crankcase and the gas tank.  Using 4-ounces of Marvel Mystery Oil to every 10 gallons of gasoline will help you engine run smoother.  It will also improve your fuel economy.  With today’s gasoline containing up to 10% ethanol, if also adds lubricity to the fuel that is lost by the addition of the ethanol.