As I often say before putting in my 2 cents worth about things in which I am no expert (which is not in anything..), this is simply my humble truck drivers opinion. Changed the crankcase and tranny oil today in my 2013 RGC from HD Syn3 to Redline. I was expecting an improvement based largely on what I have read on this forum. I was not expecting an improvement to the degree I experienced. I am not trying to sell this stuff to anyone but what a difference. The tranny operates like a completely different machine. Quiet, smooth, less CLUNK. Engine runs noticeably quieter also. Now as a disclaimer I have to say that I have been a diehard Amsoil fan for years and I don't doubt that Amsoil in the crankcase would have been a big improvement also. I will be doin' a SE Texas-Atlanta round trip on the 23rd so we will see what we will see. This forum is awesome.