At 06:17 PM 4/13/2011, Phil wrote:
>I use Castrol 20-50 in it now and have had no problems

Hey, someone who reads the owners manual. :-)

>I have an '89 Wolfie with 73,000 miles on it.  Would there be a problem if I
>used, say, Mobil 1?

Dennis Haynes is probably the most thoroughly oil-knowledgeable
person here; but the only potential difficulty I've heard of (other
than break-in issues, not your problem) is that if seals are inclined
to leak, the synthetic may not keep them swelled up.  I don't recall
anyone coming up and saying they'd actually experienced such a thing
on a WBX engine, and if it happened I presume going to a blend would
take care of it.  Here in New England the 15W50 synthetic certainly
cranks easier in cold weather.

Yours,
David