ORIGINAL: piper_chuck
ORIGINAL: MickJC
I have not heard many people supporting the use of WD40 as after run. It's a good solvent but a poor lubricant and not as effective as after-run at corrosion prevention. It is good for blowing cr@p out of buried engines.
I always use on my boat engines. Remove the glow plug, squirt some down the carb and glow plug hole, apply starter and spin it a bit. I follow this up with some light machine oil.
That's about the right proceedure if using WD-40. Never use it by itself. It can actually remove oil and 'protective additives' - functions as a solvent in some cases.
The W D stands for Water Displacer. So its great for getting moisture out of engines/assemblies/parts. But its not good as a preservative oil. Following up with some light machine oil as Chuck noted is necessary.
As noted, good air tool oils very are effective at displacing moisture, as well as protecting and lubricating. I prefer those for the after-run and storage job.