The difference between 40:1 and 50:1 will not be noticeable in terms of performance. I run my inline on 32:1. Back when people were racing these inlines, Mercury recommended 18:1 for them. Yes, 40:1 WILL protect your engine better than 50:1, but more importantly, it will make up for any mixing errors. Too little oil = dead motor. Too much oil = a little extra smoke. I'll pick the smoke.
Sure, 50:1 will do you just fine. So will 30 weight motor oil, so why do you use Amsoil?
Again, the main reason 40:1 is a MUCH better idea is to avoid any mixing mistakes. BELIEVE ME, you do NOT want to make any motor fatal mistakes. <br /><br />Woooohooo! My 1000th post! 
Actually you are only at the minimum at WOT anywhere else in the RPM range you are actually over oiled. Why do you think oil injection systems are variable. About 100:1 at Idle, and slowly goes richer as you get closer to WOT.<br /><br />Racing is a whole other way of looking at things, thos enegines turn upward of 10,000 or more RPMs, they are also torn down beween races more often than not. They do not use TC-W3 oil, and ALL OF THEM use one form of synthetic or another.<br /><br />You can say what you want, but you arnt going to get better protection unless you run WOT all the time, and I do not think you do.
