I have tried & tested a few different oils ,the dragbike I ran was 450hp air cooled & would not run at full power for more than 10 seconds without complete melt down ,it also had a turbo attached just to generate a bit more heat .The oil's I used were all fully synthetic, a straight grade SAE40w seemed the most effective ,I tried lighter 20/50w but in the extreme heat this just couldn't maintain it's viscosity& resulted in all sorts of premature scuff wear inside the engine. These particular big kawasaki are not known for having a good oil pump in the first place so I added an electric pump to boost the supply .As I had to strip the engine very regularly I got to see the effects of good & bad oil.
Oil is a very complicated science all on it's own ,to understand the terms used you need to be an industrial chemist & engineer all rolled into one. There are some very good sights on oil that give you all the standards, but at the end of the day you're still going to have to try it for yourself & see if it meets you're requirements .I have been very impressed with Motul 300v oil (fully synthetic) and used it in all my current race bike engines, 10/40 in the japanese & 15/50 in the italian engines. I have not had any clutch slip problems either, which can be caused by some high quality oil's .SAE grade is a measure of oil viscosity at a set temperature .Multigrade oil is an oil that meets the requirements of more than one SAE grade & can be used over wider temperature range .A synthetic oil is a man made oil using various chemicals which gives a more stable & stronger compound.