I carry BMW's 20W50, but I "misunderestimated" the amount of oil left in the quart I bring on road trips for my '09 GSA. As luck would have it, there would be no BMW shop on my route until Sunday. And of course, they'd be closed both Sunday and Monday.

Question: Since obviously BMW doesn't manufacture their own oil, what brand or brands out there offer the same or similar engineered characteristics to the BMW labeled oil?

I purchased some Castrol RS V-Twin 4T 20W50 - which is a synthetic - but did not find I needed to top off until I got home, so the quart is unopened.

But this poses a second question: The BMW oil is not labeled synthetic. What hell would one end up paying if he topped off with a synthetic?

Thanks for your insights.