Decided to give this oil a try. Amsoil became hard to find. It's advertised as a motor oil for older high performance engines with a added zinc package. My engine is a built 440, 11.2 to 1 Ross forged pistons, bored .60 over, ported heads, blah, blah, blah. In the summer I would run 20-50 Amsoil, then switch to 10-40 in the winter. This past summer I ran this 20-50 Syntec, through 2 oil changes. After the second oil change, I noticed a slight ticking sound. HHmm, maybe a header gasket, left front drivers side. It progressively got a little louder. This truck is my daily driver, so I know when my motor is happy or not. It started to run sluggish after a while then it became time to change the gasket. But a friend at work said NAPA now carries Amsoil, it was really hard to tell if it was a header leak or a noisy lifter, this motor has about 26000 miles on it. Changed the oil back to Amsoil. The ticking then gradually started to go away. After about 3 days no more ticking sound and she now runs like a raped ape like before. Don't know if it was coincidence or just crappy oil. I'll let you all figure this one out. Just thought I would pass this real life experience to you all on this product. Thank you for time! Later- Farmer John!!