Thanks for the reply.
Really interested to hear your experience with royal purple. I'll give you a little background on me and my experience with it.
I've helped wrench for my nephew who has raced cars since he was 12. Now I am not a engine mechanic by trade but I know the basics pretty well, and used to rebuild small race engines for a living(think gokarts) so I am familiar with how a combustion engine works.
We used to run whats called spec miata. Now before I go any further I should warn you that we used to be sponsored and get free oil from Royal Purple(not any more though). The spec miata class was run on road courses, and its just like it sounds. It is a spec class where you are very limited as to what you can do to the chassis and engine.
In an effort to decrease drag on the driveline, we would do things like clean the grease out from the wheel bearings, change diff fluid to a very lightweight fluid, collapse brake pads so they wouldnt rub, etc. It was the only way to gain as the engine was basically untouchable. We did a reverse hp pull on a dyno(this is where you run the car up to speed on dyno, shut the engine off, and let nothing but the drag on the drivetrain slow the dyno down, and it measure how much power it takes to stop it) Before mods, we used 9 hp on the reverse pull. After mods, we only used 7, which was a 2 hp gain. In fact, the dyno guy (who builds spec miatas for a living) said it was the best reverse hp number he had ever seen for a spec miata.
We did all the changes at once, so I couldnt tell you whether it was the bearings, the diff fluid, tranny fluid, brake drag, whatever that made the difference, thats why I'm really, really dissappointed to hear that it made no difference on your suv. Then again, if you gain 2hp in less drag, would that make a difference you could measure? Maybe not. So you are probably right, its probably not worth it. I know I changed to royal purple in my mercedes, which is an older car, and all it did was make it smoke and it uses oil now lol.
Just checked, my Yukon allready has the electric fan, so thats not an option. Too bad, I've heard you can gain some good hp numbers by removing it. On our late model the engine builder said it was worth about 8 hp removing the fan.
