In gereral would a group 4 oil make more hp than a group 3 oil? Well oil doesnt make hp i mean like less drag more freed up hp. I know a 5/20 would in theroy give u more hp than a 5/30 oil. How much is, my guess is half a pony? But main question is would a group 4 free up more hp than a group 3? Example, royal purple had a mustang and did a dyno with there oil and unkown oil. Showed something like 12hp increase. Oil weights wernt disclosed either. I mean maybe rp 0w20 vs a conventional 20w50 could be how they got a hp increase. The whole point of this post is my friend claims because he runs redline in his rice Honda, he has a edge agiast other rival hondas with the same mods. I told him if anything it might be worth a hp or so and not be felt by the butt dyno.