I've lived in the midwest all my life. I've seen people use POR-15 here, but it doesn't seem to work so well, and not enough for me to want to try it. My trick is to spray with rubberized undercoating, then coat with oil after the undercoating has dried. The undercoating soaks up the oil and stays moist and gives the oil something to hang on to. I've gone 3-4 years before having to re-oil and it works GREAT! I don't recommend just undercoating without oil though. The undercoating by itself will get brittle, crack, trap dirt and moisture, and flake off. If anyone has had oil leaks forever, such as the oil pan, you've probably noticed how nice the paint was under the leak, yet rusty and crusty outside of the leak area (assuming the leak started back when the paint and metal were still nice looking to begin with).