I put an F plug in my 75 AX and it really helped the transition.  Needles were not nearly as critical.  I was running it with a nice smoke trail, all seemed good but the plug burned out in a few flights.  The element was bright white but the base of the plug was oily.  DId I do something wrong?  I've been running OS motors successfully for 30 years, pretty much trouble free.  I feel pretty confident about my ability to adjust needles, but burning out this plug seems like operator error....
I want to use this plug in my new 55AX but I would like to be sure I'm treating it right.
thanks for any thoughts.</p>