What RR said.... You can run any synth oil you want, as long as its the same wt. you were running. There's alot of folks that don't realize that synth oils can go a long way, mileage wise, without thermal breakdown, which is one of its major advantages.
The price sometimes can get prohibitive, but one does not need to change that oil near as much. A T that doesn't get alot of mileage can go a few years, before the oil changes, if you heat the oil up enough to burn off the condensation residue. Alot of times, you will get more wear ( its not really wear, but folks think it is) by changing the oil too often, the bores will glaze slightly because the synthetic is so slick, it will affect the seating of the rings, causing blowby. The motor will start to smoke slightly.
That is why sometimes people in the know will run a lighter synthetic, because you do need some slight friction on the rings to have them seal.
There are instances where running synths where your seals will develop leaks because of the superior anti-friction additives. If you set your motors up correctly, you can pick up enough horses to win the races.
Alot of folks run the synth blends, which is what I do. Anti friction is good on the bearings, but needed in a few areas like, on, say rings. A motor also needs to transfer heat, also. thats why if seats are to narrow, valves and seats can overheat. Oil acts as a coolant to a certain extent in some areas of the motor, ie, valve guides and piston skirts, bearings, etc.
RoadRace motors have big oil coolers....and because of their extremely high rpms, put alot of heat into the oils....
Synths are a tricky subject....you have to know when where and what wt. to run for max. benefits.
