I wasn't having problems, but I like to change it when I buy a new to me car. I ran the amsoil for 5k miles and didn't notice any improvement. Put redline MT90 in and it was the improvement I have always had when using this fluid. No more will I be curious, redline is the way to go!
I'm running the MT90 Syncromesh cocktail in my C59. Pretty happy with it now and I'm hopping it is going to be much more cold weather friendly than straight MT90.
I switched to the mix last fall, 50/50.
And to me it does feel better than straight MT90 when below freezing.
I'm going to try Redline MT85 on the next change.
That should have approx. the same viscosity as MT90 + Synchromesh.