i switched to royal purple because i saw these videos.
http://www.royalpurple.com/video/video.html
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Well, that got me to look.
Those videos (at least the two I watched, which claimed top prove Royal Purple gives a horsepower gain) do not prove anything.
The problem is, you have no idea what the dino oil was that they drained before puting the RP in.
Taking the case of the 40 year old Mercury Comet with the hairy 1960s V8, chances are that it was running straight 50 weight dino oil, or at least 15W-40. Switching to the 5W-30 RP (he did say that was what he was putting
in) would cut parasitic losses from the viscosity greatly. It is no surpriise that, after the change, the dyno showed an improvement. But it would have shown a similar improvement had he filled the crankcase with 5W-30 Havoline dino oil. (Would 5W-30 RP do a better job over time protecting what is left of the engine than 5W-30 Havoline dino? Probably, especially with long oil change intervals. But the claim was about horsepower, not protection.)
It is as if you took training weights off the ankles of an athlete, changed his brand of shoes, and claimed that the reason he runs faster without the training weights on his ankles is because of the switch of shoes.
