+1 Amsoil metric bike oil. I like the stuff. Used it on street and track, for lots of miles. I'm gonna sound like an ad, but hear me out.
The focus with the Ams is the clutch function, and it does show. What I noticed with other full synth oils was poor clutch action at cold start (or with cold oil) and non-linear clutch action, especially with slipper clutches.
With the Amsoil, the clutch works the instant I set off from the driveway, and shifting is much more positive and I feel like there is less effort on the shifter with the Ams. On conventional non-synthetic, I found the shifter lever got harder to use and would slightly bind more often as the oil degrades, but with the Amsoil it stays very effortless and positive throughout the oil life.
I tried 300V in a few of my bikes, and once the oil warmed up, it was alright, but probably a waste of money and on my higher mileage bikes, it made my valvetrain make more noise. Amsoil and conventional oil were the only oils that made it just run better, but of course the conventional stuff I had to change every 2 seconds, but I was cheap in college so it worked out.
I've never had any rust, corrosion, pitting, or poor engine protection when using Amsoil so far as I can tell. Every time I open my bikes up, the inside of the engine is almost always spotless, nothing could be wiped off any surfaces. Even after a track crash and my other bike sitting for about a year now, inside of the engine looked just as good with only having the engine ran 1-2 times the entire year sitting, and it all looks perfectly healthy. That crashed bike has 57k miles, and my GSX-R has 47k miles, but most of those miles on my GSX-R weren't by me, so probably with worse oil, but it runs great and looks good inside.
Ams might not be the top of the heap, but it ticks all my boxes, and is more reasonably priced than Motul, and I order it by the gallon jug direct from Ams, it's cheap that way.
Just about any moto specific oil today will do you just fine, all you need to do is watch the color/condition of it, and change it regularly. I don't think there's any oil out today that would inadequately protect your engine, just change the oil and filter regularly and all will be well.
-Mike
