Quote:
By definition, in order to achieve the SM rating, the oil must be good for extended intervals. The SM standards are so high there is very little difference from one brand to another, incl WPP products.
Quote:
I agree, IF...it meets the requirements(SM) it's got to perform like any other dino etc., or very very close to it.
Keep in mind that the oils are not tested to see if they comply with the standards. The base oils have an interchange chart...a tank car of this, two tank cars of that equal three tank cars of something else...and the additive packages from the additive suppliers are certified. So what happens if the oil blender has careless or pressured workers, or if they run out of one ingredient and skip it or substitute something else? You have the situatuation of the Wal-Mart gear oil that was recalled for a reason like this.
http://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=1470524&fpart=1
Also, the additive suppliers offer lower cost additive packages...they will make compliant oil when used with the right base oil, but they'll live for a longer time. When GL-4 was first announced, ExxonMobil said that the bulk oil they supply to lube places had a shorter service life than their retail oil...MobilClean5000 or whatever it's called.
So, usually you get what you pay for. Yes, advertising is a cost that is added to the retail brands, but that is not the only cost. Better ingredients and better blending practices might also be in play.