I have had my 94 1500 Aspy for about 3 years and it has 51,000+ miles. I have always used Rotella 15-40 in most of my bikes for years. However, my Aspy since I've had it has always had some clutch chatter on takeoff after it was good and hot. I got a bunch of Mobil Delvac 1300 super when it was on sale as I have used it in my PSD before with good results. At my last oil change I used it in the bike instead of the rotella as I had so much of it. You guessed it, The clutch won't chatter now and I've tried it many times including high speed runs in hot weather. Now I'm not sayin one oil is better than the other as I've used them both in my truck for years or trying to start any kind of an oil thread, Just passing this on as my experience.