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?

it's not rust. the piston is aluminum,it cant rust. those little spots are most likely fuel deposits, not harmful. the only places rust will form is in the bearings and shaft.

Ok thanks....I wasn't thinking of the materials my engine is made of....[&:]. So should I continue using my fuel without after-run oil or should I use it?

What you may be seeing is corrosion. If it is white/gray colored and looks like rust pattern, it's corrosion. This is when I say stop using Morgans and use some other brand of race fuel with a 10-14% oil content, not the bashing 18% oil content stuff. Those need more oil because it is a poor quality oil. And also, I recommend using after run oil if your truck sits for more than a day or two without being run. If you are gonna run it frequently, it shouldn't hurt. Those spots though sound like they are from the engine sitting for a week or more at a time without being run. You NEED after run oil to prevent that.

OH, and the only things that could possibly rust in the engine are the bearings and screws. The case, sleeve, everything else is some sort of brass/aluminum/chrome alloys which will not rust.

I'm shure its not corrosion because its a dark brown colour. I am running 20% nitro with 12% lubricants. I'v been using this fuel for a long time and never had this problem...I think I might use after-run oil even if it recommends not to. I will take apart my engine and inspect everything and see how its doing....This is my stock RTR engine and soon I will be getting the EPIC .18 soon and then I might switch to O'Donnell fuel. Thanks guys