Oct. 2011 I have just now completed installing the STC from Maule flight. If you can get fuel with out ethanol it
might be something to consider. Premium auto gas is running $1.25 to a $1.50 a gallon less here at this time. I
hope to pay for the expense in a year's time. The process involves removing the Dukes boost pump and installing
an electric Facet pump that runs continuously and another pump as a boost pump. Then you cut holes in the
cowling to duct outside cool air to the gascolater and engine driven fuel pump. All to prevent vapor lock.
For some reason I am having the problem of dry carbon fouling of the plugs when using auto fuel. This happens
only on the 160HP engine not the 235HP. I'm running the mixture as lean as I can all of the time but still get
fouling. You can take an air hose and blow most of it off. It's like a graphite powder on the plugs. I have called
both Peterson and Maule and they say they have never seen this problem. I have been running 38E plugs going
to the hotter 40E has helped some. One thing that does seem to help is running a 25% Avgas blend. It seems to
clear the carbon off of the plugs. I'm going to try a 10% blend and see how that works.
1/26/2012 I have been running a 10% to 15% avgas blend and fine wire plugs. Everything is working great. At
the last oil change I checked the plugs and there was no carbon fouling.
Dec. 2013 Over the last year I have been using the 10 -15% blend and things have worked great. I have been
saving $1.25 to $1.50 per gallon. The bad news is my distributor won't be able to get ethanol free premium after
the first of the year.
Dec. 2014 I have found another source for ethanol free fuel. I have used it now for about 800 hours in the
MX7-160 and 600 hours in the M6-235.
Jan. 2016 The auto fuel STC is the best money I have spent on airplane maintenance. It's not for everyone. It will
take 300+ hours to pay for it's self. So it will depend on how much you fly your airplane and if you can get ethanol
Jan. 2018 With several hundred more hours of operation I see no problems with the STC or the use of auto fuel. I have read you want to use leaded Av gas when breaking in a new or overhauled engine. I'm not sure what that will mean if we ever get a unleaded aviation fuel. I have settled on a blend of 25% av gas / 75% premium no ethanol auto fuel for my use.