WD 40 is not recomended for the engines. Another choice is Marvel Mystery oil, available at any auto parts store. As mentioned, a few drops in the carb, prop her over a couple of times and you are done. As for needing to do this, the debate is on. I have been doing it since I got into RC 30 plus years ago and I have never had any problems with rust or engine's being siezed, so I think it is very important and I do it to every engine upon completion of a flying session. Good Luck, Dave