thats what the after run oil is for...to prevent corrosion. corrosion takes place when there is nitro left in the engine. If it's all burned out. the engine is ok without using the after run oil. I preserve the engine by means of removing from chassis, a good cleaning and inspection, I inspect through the exhaust port and check the codition of the piston and cylinder wall. I test for compression by feel. I will only disassemble If I think something needs to be repaired or replaced. "if it aint broke don't fix it". I will remove the glow plug and air filter. I use regular ATF. only a small amount is required. I put a little in the carb opening and a little in the cylinder through the glow plug hole. I use a little eye dropper available from a pharmacy or similar to put the ATF in. Then i spin it over a few times to spread the fluid around, install a new air filter elemant and a new glow plug. Put her in a plastic bag back in the box it cam in. Then when I pull it out I know she is ready to go. The eye dropper is also nice for sucking out unused fuel out of the tank after a crash or something .