Its a simple matter to borrow a tankful from one of your buddys to confirm that the fuel may be causing problems. Fuels without color dyes in them tend to be clear and without any color. perhaps a clue there but I don,t know and I am suprised also by the lightening of color rather than darkening.

Anyway if you do quit using the fuel do not discard it. It is a great commodity to keep around. Just about the best thing you can immerse an engine in for for freeing up as well as general engine cleaning after a dirt bath.

John