Horizon is so sold on using 30% Heli fuel in the Saitos, and the high oil content (24%) seems like a good thing, so I'm using it in a Magnum 91 FS in a Fokker DR-1. There is really not a lot of difference in power, maybe 200 rpm at the top end, but the engine starts, runs and idles so much better (and slower) that I always keep one jug of Byron 30% Heli on hand that's used only in that aircraft. It is expensive and messy, tho, oil everywhere, but it gives such a nice smoke trail when airborne. Bottom line: use a good quality off the shelf fuel in it and you won't be disappointed. Saitos are king of the 4s. I've never met anyone who had a problem with one.