ok, my D15 has 408k miles on it and it usually goes through 1 quart of oil every 500 miles (no smoke though) and i have used every kind of engine oil stop leak/smoke stopper/engine sealer i could find to see if they help. none did except this one! i added the CD-2 Engine Oil Stop Leak/Heavy Duty Sealer to my oil 500+ miles ago and ive yet to burn any oil!!! my dipstick is still slightly above full! this NEVER happened with any of the other ones i tried. my engine runs great too. i give it 2 big now i actually need to drain some of the oil because its a little overfull. it used to just "adjust itself".