RE: NFX fuel oil content
No problem.
I have issues with Klotz, it looks to burn and darken the piston top black, and never had that happen with the NFX, even the 35%. But, I may be need to lower the compression, just to be sure it is not me.
Klotz is used in the Sig 1/2a Champion fuel, and if I can find the NFX 25%, I would switch back as I never had this trouble with it.