This is a 2001 4.8L 1500 GMC P/UP with 65000 miles that I have personally changed the oil every 5000 miles. The fisrt 45000 miles the truck lived on Mobil 1 10w 30 with Wix or Baldwin filters. This truck has had a loud rattle in the valve train for as long as I can remember. So at 45000 I switched to 15w 40 pennzoil long life and it did help cut down the clatter when hot but not gone (added 10psi oil pressure at hwy speeds). At 60000 I ran a wix filter 5 qts Pennz LL and 1 qt of Lucas HD oil stabilizer. No change in noise maybe a little higher oil presssure cold and warming up. But when I drained it out the magnet on the plug was clean !!!!!!! This truck has had dark grey residue on it every time but this one I make a point of cleaning it off with a clean paper towel every time just to monitor the amount (the first two changes the magnet was fuzzy). This time CLEAN nothing but oil ???? Was it the Lucas.