ORIGINAL: Jim Thomerson
A counter story. My son had a timer failure and lost His Fox 25 powered free flight at the 1980 Dayton Nats. It landed in a tree and spent the winter there until it blew down the next spring and the people who found it contacted me. The engine had no rust or corrosion. It had been run on all castor fuel. So maybe one doesn't need after run oil after all.
Jim, that would seem to reinforce the experience I gad with the engines left fordecades in the dank basement after having been run on 100% castor. I might add that some external parts, prop washers, head bolts, etc. were rusted but nothing internal.
For what it may or may not be worth all these engines (Fox, K&B, Johnson, Holland and Holland, Cox, ST) were flown control line or free flight and thus were always run dry, either through running the tank dry or having the fuel cut off by a pinch-off timer.
As a matter of current practice I always run my engines dry after use.
My practice of running dry and use of ARO may do no good, but I have a couple of hundred engines that over the years have never shown any sign of rust, rot, corrosion, or running over at the heels
As running dry and adding a bit of oil requires such a minimal effort and expenditure, with no possible adverse affect I am at a loss yo come up with any reason not to do so unless one simply does not wish to. This being a merely hobby that is reason enough.
jess