CASTROL POWER 1 RS 4T 10W-50
this is not listed on either the US nor UK castrol sites
It is listed on the continental european Castrol sites
Of course since 1994 when I bought the first Skorpion, names and formulations have changed.
Basically, I have never used anything else and the blue bike, back on the track and ulling better than ever, still has the first valves and guides with 90tkm.
Most will know that this thing has always gotten flogged and that it had 59hp at the rear wheel. Has more now...
I religeously change filters every time I change oil, not more than 3000km and always use K&N filters.
US and UK sites list CASTROL POWER 1 RACING 4T 10W/40.
I assume this is the same oil save for the SAE rating which probably reflects the much more sedate driving habits and speedlimits in those countries. I can't think of any other reason. From my friends, I am aware that real-life there is different, too. When I was still living in the States, the only ones that adherred to the speedlimit more or less were the car drivers. Trucks ran pretty constant 75mph on the Indiana toll road and the Interstates, Greyhound busses more like 85mph. Bikes, when you actually saw one bigger than a CB72 (Probably a Triumph, if lucky a B34 Clubman), were in another world. I use the "commute" to Chicago from Ann Arbor, slipstreaming a Greyhound with my Consul that couldn't possibly go that fast on its own.
OT - sorry
In the Mondial and Laverda I use Motul 3000 20W50 which is mineral oil. Both have or can easily have slipping (to say the least) clutches. The Castrol does not work, let alone car oils. Probably best would be one of the classic SAE50 racing oils.
Be careful with car oils. you can get lucky - or not. Manufacturers make motorcycle oils for very good reasons. They don't do it to con the customers. That said, if you have a Ducati with a dry clutch, you can run any car oil of suitable quality. We here don't have such things
(I do but use the same Castrol) or at least we aren't talking about them here. In my MZ racer, I had problems with the clutch when I tried hi-tech car racing oils, both Castrol EDGE FORMULA RS SAE 0W-40 and Silkolene Pro S 5W-40.
I have only limited personal experience with
Fuchs products, but I know they can be highly recommended.
Above all don't mix oils, especially not car and bike oils if you are using anything syntethic or partly so. There should be no danger if you are using straight-forward mineral oil and changing it often.
Another tip (not my invention by any means): put a healthy shot of synthetic 2-stroke oil (or castor oil) in the gas tank when you fill it up. Buy a can of propriety 2-stroke racing oil and use some small (±50cc) plastic bottle you can put in the tool box or just use the little plastic bubbles of chainsaw oil (not the stuff for the chain of course) you can probably get at the gas station. It won't improve performance. It does help keep the carb slides lubricated and it helps the valve stems, too. This has always been common usage with 4-stroke racers, so common that it is generally never mentioned.