Perhaps you should do a bit more research into the products that Fuchs supply/manufacture, the Pro S that is so popular is the Silkolene Pro S rebranded as Fuchs own Silkolene, and Silkolene know thing or two about performance oils :thumbsup:Fuchs are primarily a industrial lubricants manufacturer. I would use a OEM or Mobil lube given the R&D money these guys spend on lubricants. You may get away with it but why take a risk with your engine
Viscosity wise in an R35 there is no need to go above 5w-40 unless temps/modds/use is extreme. The engine is designed to run on SAE40, the only reason Mobil 1 0w-40 is recommended is due to the fact the best Mobil have to offer around the SAE40 viscosity is the 0w-40 (Porsche do the same, they are holding hands you see).