just my 2 cents. Figured id let every one know what i think. From new to 70000 miles ive run castrol gtx 5w30, never had an oil related problem, other than a few leaking mopar oil filters. Since it was new ive had the dredded "hemi tick". Any way 2 days ago after only 700 miles on new castrol my amsoil order cam in 7 quarts of Semi synthetic and an amsoil filter. i was told by a friend for the first 2 or 3 oil changes to use the semi then switch to the full, i guess to slowly recondition internal seals. So out with the old and in with the new. Fired her up, smoother, quieter, and as for the hemi tick???............What hemi tick i can barely notice it. she also runs a little cooler when fully warm. SO plus one in my book for amsoil......................Oh and yesterday i had 4 brandy new cooper ltz's mounted and ballanced. And compared to the factory suckyears, these are like riding on tank treads , and have about the same traction as em. I love these tires.

 

I had similar results when I switched from Mobil 1 to Royal Purple. The Hemi-tick became barely noticeable.

Just a word to the wise for MDS guys, Amsoil has been shown to increase viscosity over time. I'm sure it's why it lasts so long, but the tolerances of an MDS Hemi are such that I'd not recommend it, or if you do use it, don't go much over 6000 miles between changes...