Ok, I'll throw out the counter point.

For years, I never bothered to run the engine dry or use after run or anything, and never had a problem.

However, recently, I got in to flying combat. In combat, it's not uncommon to fly a plane just once in a trim flight before a contest and never again that day. Like 2min flight, max. All of a sudden I rusted a couple of sets of bearings. Not in my primary planes, that get run alot, but in the backups that run once in a while.

Now I use Automatic Trasmission Fluid as after-run and I've had no problems since. I use a good squirt of it too, none of this wussy "3-4 drops", that's not nearly enough to coat anything.

Ok, so why did I suddenly have a problem, and why do these guys who burn fuel by the drum never have problems? I think it comes down to engine heat. An engine that is run at full temp, and shut down with out a prolonged idle will (I think) boil off any remaining fuel in the engine before it cools off, leaving nothing but oil, and so it doesn't rust. Run an engine just once, for a short bit, or run it at idle for a long time, and the engine does wind up with liquid fuel in it over time. And that attracts water from the air, and leads to rust.

A couple of other factors I've though of that might, or might not, play a part. Some engines use cheaper bearings and metals in some of the parts than others. I haven't done a "study" but it does seem to be more of the less expensive engines that rust up.

I haven't heard about not plugging up the exhaust and carb. I have started to do that to keep stuff from dripping in the car these days, something I didn't bother with in the distant past (before I was married).

But I do think the biggest difference is how you run the engnie, and how often.

That's my story, and I'm sticking to it.