Originally posted by Top Gun 777
Normaly if your piston s white clean-it means it didn't work yet. Even after 2-3 tanks of work on racing tuning, it should became dark brown and later black. It doesn't supose to collect varnish and if it is, as Slotmachine mentioned-that fuel isn't the best. Try to use some very well blemded as O'Donnell, Bayron. I have very good expirience with them. Also, you can contact to Stefan and if you live in his area, he is blending very good fuel, I recomend it to you.
Is the dark piston surface a bad sign? i remember with my VoneS engine after 3-4 litres the top surface of the piston was still gold and looking like brand new!!! now with my MR-12 it went dark within 1 litre or so... but i have changed fuels from a 15% nitro 18% lube oils (voneS) to 16% nitro and i think 10% or so lube oil (MTX-3 mr-12)