I have a very interesting development.....quite pertinent to this BMW oil discussion.
First, let me qualify that once upon a time, not so very long ago, I was the Plant Engineer for the Lubricants Complex of a major refinery in the USA. I used to know a thing or three about motor oils. If I ponder it awhile, I might could again.
ITSATDM is very correct: Much has changed in the blending formulations of motor oils over the past 25 years....specifically among the "additives". For a motorcycle, stick with a JASO rated oil, given the choice. An auto parts store is a great place to find a cheaper supply ( if you're a shrewd buyer ). In a pinch, don't sweat it, most anything will get you by (with some discretion).
Anyway...back to my F800. At 15,000 miles, a consistent slow oil leak had developed on the right side of my engine up high. I traced it down to the weep-hole beneath the water pump. Seems there is an Oil Seal on the water pump shaft that can be prone to leakage. I acquired a new & improved seal for future replacement when I finally decide to dig in and check my Valve Clearance.
I had been running various synthetic blends of oil for some time, to help smooth the shifting action. At my next oil change, I swapped to a conventional BMW branded 10w40, purely for matters of convenience, no other consideration (long story).
The oil leak stopped! Has not leaked again during the next 5,000 miles (including another oil change). Yes, I stayed with that same oil choice...because its not leaking. This particular oil seal is obviously much happier immersed in this particular blend of conventional oil than the synthetic blend I was using. Might have worked with any brand of conventional oil, though each lubricant complex has its own secret recipes for blends.
Various rubber materials can react differently to oils and additives. Just something to keep in mind should you encounter a similar issue. If you have a weep or leak, try changing oil types (first), oil brands (2nd) for a potential easy solution. The change won't be instant. It took about 1,0000 miles over a couple weeks for the leak to completely stop, as the rubber material reacted to the change....making it swell and seal.