Don't take the piss here, it is a genuine question. I have some left over 75W90 GL5 from the R1200GS, this is for the gearbox, that I have used to fill the R1100S gearbox after an oil service in time for the BMW Club track day. I do this a few times a year to keep the mechanical bits (engine, gearbox and final drive) sweet and keep an eye on any mishaps within the said bits. So instead of purchasing the 80W90 GL5 as recommended by BMW I thought what harm can be done. The R1200GS has more power than the 11S so it can do the job. It is not that I will use the bike outside of it's temperature range. The lower rating just means it will flow easier (lower viscosity) at low temp but still have the same properties at the higher temp. Anybody care to comment. For me I'm more concerned with the higher temp as the gearbox will be working harder as for normal road riding.
