I know for a fact Amsoil has many 100% synthetic oils including one for dirt bikes that I really want to try out as it has a special additive package for longer clutch wear (something I'm having an issue with the 600). It was one specifically recommended to me by the petro engineer (even though he leads oil development for a competing company)
According to the data sheet 300V is fully synthetic (100%) and is an Ester-based oil with a shear stability index of 4.19 - this is not bad. Not the best but in the upper range with the better oils. I will definitely try it if I find it at a reasonable price. In fact, I think my cousin is a distributor for them so I should be able to get it quick and cheap.
From the Motul site;
"300V Factory Line lubricants are especially formulated for the severity of racing applications. Based around the Ester Core® technology, 300V Factory Line lubricants provide the best engine response and protection at very high temperatures and RPM, throttle feedback, clutch feel and ultimate gearbox protection. Four viscosity grades are available for track/road applications
with 100 % shear stability and constant oil pressure and two viscosity grades are available for off-road with optimal traction."
I know on the other bike Amsoil showed no performance degradation over time with respect to power decrease caused by shear. I would probably take the 300V claims at face value as, generally, at that end of the spectrum they are all really high-end oils whether Amsoil, Red Line, Mobil 1, Motul etc.
I'm currently testing out Mobil 1 5/50 auto-grade oil in the 600. This has been widely used by a lot of people and many claim it's the best even though it's not a JASO rated motorcycle oil. It lacks the Energy Conserving rating so most assume it's safe. One thing everyone comments on is that the bike shifts well. It does. But I think there's an issue there.....
I frequently do WOT runs often up to top speed. This means shifting clutchless in the fat or the torque curve. I typically take 20 ms to shift in those circumstances. I'm finding that with the Mobil One auto oil the clutch is slipping. I have a lot of problems with clutch life, on the whole, due to the way I ride.
With my other bike I had a new Carbon Fiber clutch made up for it by a leading clutch company in the UK. I then designed and manufactured new springs with 400% greater clamping force. The difference between cork and Carbon Fiber is also about 400% greater friction co-efficient. This got me (more/less) 800% greater clamping power. That got me much longer clutch life.
Bear in mind, all of this research came about through experience racing other bikes for 6-8 hours. I would beat them handily in the morning and by afternoon they were riding next to me at WOT in 6th and then by late afternoon they were passing me with no problem. This is what led me to oils, clutches and ultimately making my own springs.
I just got into the 600 a few months back and last month put a new clutch and basket in it. Already, the clutch is showing signs of wear (about 10,000 kilometers). I've already contacted the firm in the UK with an eye towards getting a proper Carbon Fiber clutch for it as all companies seem to have are Kevlar-based units. This really surprises me as the 600 is more/less one of the defacto high performance racing machines out there. You would think it would be the very first model that everyone starts out making a Carbon Fiber clutch for.
Instead what I'm seeing is nothing but cheezy Kevlar units. I beta tested a Kevlar unit provided by that company a few years ago and all it took to kill it was one high temperature experience.
Kevlar rolls over an dies as soon as it's heated up. One shot is all you get. The Carbon Fiber clutches really don't mind heat and high RPM. I found it was nearly impossible to get a CF clutch to slip and I could not cook it. I put 8 or 9 through the bike and every one failed the same way - hard to find neutral. That was it. So I could ignore it and go back to Nitrous shots with no slippage. The only reason for replacement was ease of finding neutral.
I'm digressing but I suspect that Motul 300V may be the equivalent of Amsoil. Knowing it's 100% shear stable should mean you can save some bucks on frequent oil changes though - although shear stable doesn't tell the whole oil story. I personally ran Amsoil all the way out to 7,500 km's but I usually changed it somewhere in the 3,000 km range. This was on an engine with a total oil capacity of 1.3 L, no oil cooler, no oil filter (strainer) and being over-revved on a more/less permanent basis by 2-3,000 RPM. It was not uncommon for it to spend a 6 hour day at +10,000 RPM with jaunts up to 13,500 and even 14k. The factory red-line on the engine was 11,000 RPM.....
That level of abuse, combined with +100% power increases with Nitrous, really showed off Amsoil's oil! And the Nitrous on that engine would last for a very long time (small displacement and dual tanks).
I'm doing a lazy Sunday ramble, but 100% synthetic oil is essential in any engine a person cares about and especially motorcycles. The difference is huge. Also, I believe synthetic also runs about 10 degrees cooler then conventional oil. If we understand that heat is the enemy of every clutch other then CF units then this is a very big benefit to the clutch alone.
Sorry for the really long post but this is an area I have a lot of experience with so I thought it would be useful to share it.