I think that one of the biggest avenues of moisture being introduced into the engine is from the fuel. Ever notice the condensation that forms in a partially filled jug? That is one reason I never let my jug sit in the sun at the field. My truck has a cap and thats where it stays, in the shade. Buying by the case, I keep the remaining stock in a cool dark area. One other way to avoid condensation is to transfer from another jug to keep the one that you bring to the field full, whenever possible. I've often thought of one of those collapsible jugs that won't allow air in as fuel is pumped out. Like a bladder. As others have reported, I have other engines using the same fuel and under the same conditions that never rusted out. Joe