Originally Posted By: MalfunctionProne
I have RP oil and RP oil filter on the truck.
Redline is a better oil, but higher HTHS, so I put the Purple in there. Silky smooth
Royal Purple gets beat on because it seems to be a somewhat goofy (Purple?,) gimmicky, and ezpenexpensive oil. BUT... if you DO LIKE I DID and GIVE IT A SHOT.. You tend to say "You know what? This oil is amazing."
As far as freeing up internal resistance and lessening friction, it probably does with the oil under its purple guise, in some kind of way better than about any oil.. except Redline.. which is why I mix them. They just don't tell us a whole lot about it.
Give it a try. It is awesome.
Dude, I've run everything from 0w-20 to 5w-40 in that same engine and it doesn't care. Do you know why? Because it is pushing around a transmission that is the size of a Civic with a transfer case the size of a Yugo attached to it, which in turn is attached to two driveshafts, which then attach to a 9.75 and 8.8" set of ring gears, all to motive a vehicle that weighs north of 6,000lbs. And it does it with 260HP. There is so much drivetrain going on that pretending that the minuscule difference between viscosities has any significant affect here is ridiculous.
Sure, I MIGHT be able to see some guy with a manual Corolla notice some more "pep" with a lighter oil (which actually translates to next to nothing on a dyno, but anyway), but you are so far removed from that sort of direct connection with the Expedition, and insulated by so much girth and driveline that saying there is a difference is being dishonest. I even measured fuel economy and could observe absolutely no change.