As of March, 05, 2010 I started running my 6/1 on a diet of 50/50 crankcase oil and #2 furnace oil. I have abt. 20 hrs on the mixed fuel and have not seen any difference in the way it's behaved. I run it from the original CS. tank with no heating of the mixed fuel, it has so far started without a hitch, with a temperature as low as 21F, electric start of course!! That said, I did remove the head before the start of the mixed fuel and noted the condition of the piston top and the injector. One thing I should mention is that I fumigate with propane on an intermittent basis, there was no prior plan in place with the fumigation of propane and I will continue to do so as I have done in the past.
The low level plan is to run it 10 hrs every week (not acccounting for power outages) for the rest of the Summer. I will before the snow starts in the Fall remove the head again and check for carbon buildup if any. If at this time there is a carbon problem the rings will also be checked.
R/B