I too always wondered about C11... The residuals from combustion seem to be terribly hygroscopic.... I've seen rust on almost every part post-combustion, but nothing on the intake side... Its not the fuel itself, it appears to be after its burned....
If I know I'm not going to run the car for a while, when I pull it in the garage, I open the hood, then kill the fuel pump and work the throttle on the carb while I spray in the oil, and keep the Revs up until the float bowl is dry and the engine dies. This has alleviated all of the issues. The white smoke and odor of this operation wafting up through the house is not at all appreciated by the wife however....
