Glow engines need after-run oil regardless what the fuel label says. And that's a simple fact. This photo is from an engine that had LESS than 1 gallon run through it. The label said "Contains Rust Inhibitors". Well, I guess it didn't work...
At the end of the flying day you should:
(1) Drain the fuel tank and
run the engine dry.
What are GOOD After-Run Oils?
Any oil is better than none at all, but are some better than others. Some
people use ATF (Automatic Transmission Fluid) others use Marvel Mystry Oil. And then
there's the stuff the hobby shop sells. I prefer to use Klotz Techniplate. In my 37 years
of R/C Modeling I haven't had a single corroded bearing when I used Techniplate
consistantly. No matter what you use, use it regularly at the end of the day. Glow fuel
absorbs moisture aggressively and will rust your bearing in less than 12 hours if it
happens to be a humid day.