Running decent quality oil in any motor is definitely the best insurance policy you'll ever buy. I was a "Cazzy R" racer back when, and if anybody wants to argue about R's lubrication qualities, you must have a screw loose!! It does however leave a lot more internal cylinder deposits than any Synthetic oils, and that's important on 2 strokes. This requires a lot more diligence in regular maintenance - a true fact.
Most of my racing experiences have been with either motors with separate primary drives, or dry clutches, where I would use a different oil for a wet clutch and I was pretty reluctant to believe Synthetics were the 'way to go'. After experiencing using a 100-1 premix situation on Trials bikes (both modern and Classic) using Synthetic oils, I became pretty interested in why it works.
In simple layman's terms -- try frying an egg in petroleum based oil, then do the same with a good quality synthetic ---- I'd eat the synthetic one first!!
There have already been a few scientific facts bandied here, that only cloud the issue of what oil to use in certain conditions, so -- here's my humble recommendation.
Back in 'the day', a lot of engines used 'communal' oil for both lubrication for the crank/cams/top end, as well as the clutch/primary, and I always considered it was that way for 'job security' for the factories, as when the clutch plates shed both friction and steel bits, it all found it's way through the oil pump -- and ultimately the rest of the engine. Those guys were pretty sneaky!! Many wet clutch bikes still use the same system, although materials and OILS have come a long way, and the attrition is definitely not anywhere as bad as it used to be, it's still an area where regular oil changes -- no matter what oil you are using are necessary to keep your engine in top form as long as possible.
IF - a modern manufacturer stipulates a certain oil --- DON'T argue.
IF you have been running the bike on petroleum based oil for any length of time (thousands of miles) -- keep using the same oil until you need to rebuild the engine.
Reasoning here is from my own findings, that seals get 'conditioned' to the oil they were 'born in', and if you change from petroleum based to synthetic after major mileage - expect problems with leaks.
I've seen it happen a few more times than it takes for a 'fluke' to rear it's head!!
My race bikes are fired up with petroleum based oils -- just to get ring seat, and immediately live on Synthetics -- usually Catrol Syntech -- a great oil - as expensive as it is!!
All the modern wet clutch bikes I deal with, I stipulate Mobil 1 4T 10w40, which is fully synthetic and has no silly "friction modifiers" or whatever nonsense most Synthetic oils blart about.
I spent some time under the tutelage of a friend that worked in the oil business for a long number of years, raced (reasonably successfully) for a good few years, and heard all sorts of "Old Wives Tales".
Bottom line --- Don't short-change your motor with cheap oil.
If it is happy where it is -- why change?
Ride it hard - and put it away dry!!
Cheers,
Brid.