Hi Robert
I do not believe it's a point that Rotax has to defend, i know it was tested on dynos and in aircraft with many different test engines. It was used in different aircraft and prop combinations. The oil had to function at far higher oil temperatures than others and work with leaded fuels as well. I personally would use it over Sport Plus 4. Sport Plus 4 was problematic with the 916 and that's why they developed the XPS. Naturally you are welcome to use whatever oil you want but that is more risk than using the one they tested. Just my opinion. If you come to Oshkosh the XPS people will be there again and last year they were very open with all the data of what was done. They will have people at the Rotax booth and at the short presentations at the booth during the week.
Here is the statement from Rotax:
" XPS Full Synthetic 5W-50 Aviation Engine Oil was designed specifically for Rotax Aircraft engines for the best performance, reliability and safety. Over two-years’ worth of development, forty tested variations of fluids, 20,000+ gallons of aviation fuel and 12+ fired engine tests led to the final formulation."
Cheers
