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I find myself with two litres of “Fuchs Silkolene V-Twin 80W-90 semi-synthetic extreme pressure transmission fluid Maintain”. While the oil classification matches that recommended for the R1100S (i.e. SAE 90 API class GL 5) it also says on the container "specially formulated for Harley Davidson and Metric V-Twins". By chance would anyone know what "specially formulated" means and are there any advantages or disadvantages to using this in the gearbox of the R1100S ? Thanks.

Hello All,
I'm replying to my own original posting having found the the answer to my query, and in case anyone out there would be interested in that answer.
It seems that the Fuchs Silkolene V-Twin 80W-90 transmission fluid is considered ideal for a R1100S. The "specially formulated for Harley Davidsons and Metric V-Twins" comment on the container refers to the fairly high dose of ZDDP in the formula. You may know (I didn't) that ZDDP is an anti-wear additive found in most oils. However a lot of modern oils have reduced the levels of it as it can upset modern emission systems, but older engines don't have that issue, so ZDDP is a good thing for them. (This information comes substantially from the helpful technical people at Opie Oils).
As I write this, the last of the old oil is draining from the R1100S gearbox and the new Fuchs Silkolene will be going into it shortly. I'll update this in a few weeks with any findings.
Robin

Interesting.

I seem to remember that (I think) Grommit recommended Harley Davidson engine oil for the R1100s, as it basically was the same type of engine and was very highly thought of.

Maybe was a 'black' oil so could have had a trace of something like Molybdenum Disulphide in it?

Intrigued as to why a gearbox oil could "upset" a modern emission system?
Engine oil yes, as the crankcase and head breathers would be routed back into the intake, but gearboxes aren't.

Hello John
Good observation - when referring to upsetting modern emission systems, I was assuming that Opie had the ZDDP in engine oil in mind at that point in their comment. It has been reported that zinc (the ‘Z’ in ZDDP) and phosphorus emissions may damage catalytic converters.