I've used Castrol 20-50W during the first 3500 miles on my '06 Classic - but the case is running low. I've seen the disussions on additives (or negetives) in the lastest oil specs and the effects on old engines... happened to see a gent at Autozone or Pep Boys (don't recall which it was) with a gallon jug of Castrol 20-50W 4-Stroke Motorcycle Oil... haven't checked it out, yet, but it may be Castrol is making a real effort to make something usable for old motors. Even if it's just a different label, I'll probably switch 'cause I'd rather use a gallon jug than have several half-empty quarts... I changed the oil (and filter) at 250, 500, 1000, and 2000 miles, and haven't used two whole quarts yet! Guess the only way to completely drain the motor is to remove the timing-side case, and that seems a little extreme to me...
Mike and Stumpy in Michigan