Winter Storage with Full Tank Of Gas or Not?

babock wrote:
Leave the tank without filling and just fill up in the spring.

Condensation in fuel tanks is a myth. If you had a 100 gallon fuel tank and it was completely empty except for 100% humidity air @ 70° and it all condensed you would get a grand total of 0.22 ounces of water.

The math is correct, the logic is deeply flawed, and since the OP is in Minnesota not California he probably has a valid concern.

The calculation of water content is for a SINGLE tank full of moist air.

Fuel tanks breathe, as the liquid and air warm up they expand and push out air, that evening they cool and condense pulling in replacement air which is generally very moist and the cycle starts all over again. This happens all year long, anytime it’s warmer during the day than it is at night.

babock wrote:
SeaFoam is snake oil. It contains oil,naptha and isopropyl alcohol...that's it folks! And you don't want to run it on engines with O2 sensors..it degrades them because of the oil content.

Call it anything you like but it works, and it works well. It does NOT harm the O2 sensors, in fact it cleans them.

GM sells, or at least did the last time I checked, a ‘top engine cleaner’ which according to the SDS is almost exactly the same formula as SeaFoam is. I doubt they’d tout something as being good for your engine if it would cause damage?

The ‘oil’ is lighter than kerosene and when diluted to the extent it is in a fuel tank is a very tiny percentage of what goes through the engine.