and most the available synthetics run that or an equivelant compound. A short list I just found; Castrol Syntec 20W-50, Valvoline VR1, Royal Purple XPR, Red Line, Mobil 1 15W-50 and Amsoil Synthetic Premium Protection
The stuff I run in my bike is around $10 a quart, luckily synthetics for cars can be had for $25-30 for a 5 quart jug, vs about half that for a conventional. Not sure how much the extra the additive is, but the benefits of synthetic are why I buy it. Again, you seem pretty set on your decision to use an additive so I'm only trying to offer the alternative view
