Don't know what kind of ride you have, but on our Goldwing I now use Shell Rotella T in the blue jug. It is about $15.00 per gallon at Wally World. I used to run Amsoil, even got the membership at the Davis Rally for the discount price. The stuff is good, but mighty spendy. For giggles, I sent in an oil sample for analysis, and again after i had done a few changes with the Rotella. At the same mileage both were up to spec. The Rotella seemd to shift smoother for some reason. I check the feel, smell and color of the oil to deterine when to change oil. Even with the Amsoil I have never gone beyond 6000 miles. About the same with the Rotella.
I think the oil holds up, it is the contaminates like combustion gasses, metal wear and such from the engine that are bad.
If I remember, the Amsoil is a pure synthetic, and the Rotella starts with dino oil base stocks. Can't see where it makes much of a defference.