[UGS_Tom]

75W-90 is recommended by our trustful bavarian engeneers - why not just do so?
I doesn't matter, depending on your availabilty. Difference is only the price.

 

[UGS_Tom]

...but if you check the German NineT forum, there are quite some guys swearing using 75W-140 as their gearbox and bevel gear oil.

Do they say what the advantages have been ?

... let's say it is still 50:50 (in many Boxer forums) - some mention a smoother shifting with 140... some not !? Could be useful at higher temps - ..or not !?

...

...