So forgive me for dragging up an old oil thread, but this is the reason I found the forum.
I was looking for an answer to something that I can't explain, and google led me to this thread, which has had a decent technical component to to.
4 years ago, when i bought my RM 125, I was trying different oils (mostly an availability thing) and ended up with some Belray H1R. I immediately noticed a power increase. A significant power increase. I didn't believe it was possible, so I did some back to back testing. It was a very obvious, and very significant difference.
A few weeks ago, I ran out of the Castrol GP 2 stroke I've been using in my vintage bike, and my dealer had a deal on Belray MC 1. I tried it, mixed at the same 40-1 and noticed a significant power increase. Exactly the same as the above, I was able to duplicate it.
Both times it was Belray, and both times the difference was significant. If somebody told me the same thing, I probably wouldn't believe it. The first time I chalked it up to possibly jetting, or the way the oil contributed to combustion, but exactly the same result twice on 2 different bikes.
Can somebody explain what's going on?