While I was searching for info on 5W-30 PUP I came across an old post stating how quiet his engine was after using this oil. I just used some old PUP that I got in WM a few years ago and it had the same effect on m '02 GMC SD 6.0. I use ALL different top brands of oils, Mobil 1, GC, Valvoline etc. and none has ever taken away that noise like this oil does. The jug had a $64.xx (??) clearance sticker price on it but it came up much less. Is the old version of this oil different in quality than the newer one, it's now $24.xx ?