Any reason why not to run 10w30 synthetic racing oil in my new rebuilt sb400?

[gmachinz]

Too much technical jargon for any engine that isnt a sponsored race motor imo lol. I used to be an amsoil dealer-my rep while they wil always claim to be the best rated synthetic motor oil, he admitted that Mobil 1 is right behind them quality wise. Two things are should be looked at before anything else from my experience:

1.) Film strength
2.) Rate of evaporation

Film strength refers to an oils' resistance to being squeezed out from between 2 surfaces ie bearing/journal.

Rate of evaporation refers to how high of a temperature the oil can resist breaking down due to extreme heat-this is the brown yucky haze you see covering the insides of your valve covers like a slimy film-oxidized oil.

Most companies dont promote technical info because frankly, most oils wouldnt rank very high. But I am aware that Amsoil is as follows:

Film Strength 600 psi
Rate of Evaporation/Oxidation 1200F

Everybody seems to get hung up on detergents and such-I prefer an oil with extremely high film strength and resistance to breakdown-and so consequently these two pieces of criteria eliminate ALL conventional oils and most true synthetics. And look at the label of your chosen synthetic oil bottle-if it says Group III base or anything simialr-dont buy it. Group III is still a carbon basestock and is moreover just dino oil chocked full of synthetic additives to make it "mostly synthetic". This is exactly why Mobil sued Castrol over its Syntec claim back in the 1990's.