Last year prior to putting my F150 out of service for repairs, I had noticed my dipstick had rust on it, heavily. Now today I got my truck back in running order, but I was unable to remove the dipstick. It must be rusted in the tube. So, what caused the rust to start? My oil from the pan looks normal, not milky like water contamination, but must be moisture coming from somewhere. Anyone have an idea? Thanks for your time.

 

I'd guess that you aren't driving the truck far enough to get the engine completely warm very often. And if you live in a humid climate the daily temperature fluctuations can cause moisture to accumulate, and that is probably happening on the dip stick. If it sits dry long it will rust that metal.

 

Welcome to the forum, carlforman!

My mentor, when I was growing up, taught me about the importance of getting the engine [oil] up to operating temperature [can take 20+ minutes]. He said that everytime an engine is shut off, as it cools the conditions in the crankcase are much like a "rainstorm".

As a side note, he changed oil and filter in all his vehicles every 2 months and did not worry about the mileage. This was, of course, before improved oil [both dino and synthetic] was introduced.

 

Yes, a thermostat that is missing or stuck open will also cause this problem.