Today I was cleaning my truck so I took out my glow plug to test if it was good or bad. I looked inside the engine and I was little spots on my piston wich I think is rust. I don't use after-run oil because I'm using Morgan fuels wich say they that I don't need after-run oils.

Quote " Do not use After-Run oil with our fuels, our Rust Preventer is like a built-in After-run oil." end quote

So I did what they said but i still think there is rust forming. The only way I can really tell is if I taske my engine apart but thats going to have to wait since I'm busy. So do you think I shouldn't use after -run oil or just screw what they say and use it?