I'll readily admit I'm Mr. Amsoil, Dr. Bias. But with your type of driving synthetic oil would not only be best for your engine, it would save you $.

But if you insist, I won't bad mouth dino oil. I'll stick with the facts on dino 20W-50. DON'T USE IT. The viscosity numerical spread is just too much for petroleum oil to handle narurally, so the blenders add viscosity enhancers for the summer number (50), which typically consists of a thickener that can be considered unstable/not long lived at high temps and pressures. By products include nasty sludge and varnish. On the winter number (20) this is acheived with pour point depressants (ie solvents), which rapidly out gas from the heated oil, only accentuating the breakdown and thickening of the oil. Your owners manual makes no mention of 20W-50 for good reason. (PS the above is NOT applicable to good synthetic 20W-50 which can make the spread without gross additives)

Really I'm not trying to sell anything to you - but if you shoot me your snail mail address, I'll send you a neat 8 page description of motor oil classification (SAE and API) with all kinds of good stuff about viscosity, volatility and just good light reading on motor oil. I promise you won't be added to any mailing lists.