I don't know about its current formulation (OTOH, I doubt it's been changed in 5 years) but a few years ago Fast Fours and Ferraris Magazine did a short comparison on synthetics in re Noack volatility test...Castrol Syntec was the ONLY synthetic that failed..and it failed miserably. Some 12-18 percent of the test sample evaporated during the test cycle.

Upshot is the stuff is probably better than dino oil, but you'll lose a quart of it in a 5 quart engine in about 3000 miles.

Try Amsoil 10W-40 marine synthetic....it's got the best price point of the amsoil synthetic oils and an excellent anticorrosion package for lowtemp/seldom used marine engines that often sit for a week or two between uses.

I wouldn't use 20-50 unless the engine was way old and needed an overhaul...and in that case it probably would leak so bad that synthetic would be a bad investment....Can leak a lot of dino oil for 69 cents a quart!