I’m not in total disagreement, but the urban myth may be more of a Great White North myth. In that, when it gets cold out it stays cold until spring. But otherwise, when it get cold at night and warms up in the day, it best to keep the tank either full or empty.
The reason is that a metal tank with some liquid will dehumidify the air inside (and outside) the tank during the daytime when ambient air starts to warm relative to the night time lows. Think about a tank half full after a cold night. The cold fuel is a big heat sink and will keep the tank fuel and metal container much colder than the warming daytime air. Warming air + cold metal surface = condensation, i.e. cold sweat. A full tank has less condensing surface and less air inside. An empty Aluminum tank will warm and cool with ambient air so there will be little if any condensation. I guess one could close up the tank (i.e. close of breather line) to try to eliminate the reoccurring condensation, but that’s likely not as easy as it sounds (and end up being a bigger PITA than filling the tank). With any luck, Global Warming will rid the Canadians of some urban myths…. - Paul E. 1981 C&C Landfall 38 S/V Johanna Rose Fort Walton Beach, FL http://svjohannarose.blogspot.com/ > On Oct 25, 2018, at 4:12 PM, [email protected] wrote: > > > Message: 1 > Date: Thu, 25 Oct 2018 19:41:45 +0000 > From: Marek Dziedzic <[email protected] <mailto:[email protected]>> > To: "[email protected] <mailto:[email protected]>" > <[email protected] <mailto:[email protected]>> > Subject: Re: Stus-List Filling diesel tank > Message-ID: > > <byapr11mb2934ad3a98b329934abb0ae6ce...@byapr11mb2934.namprd11.prod.outlook.com > > <mailto:byapr11mb2934ad3a98b329934abb0ae6ce...@byapr11mb2934.namprd11.prod.outlook.com>> > > Content-Type: text/plain; charset="utf-8" > > Consider not adding the fuel. > > This is an urban myth that the condensation would add a lot of water to the > fuel. The water in the fuel tank comes usually from the leaking fill hose > cover. If you don?t believe it, do some calculations (;-). > > Depending how much you motor, if you keep topping up the tank, you may end up > with a lot of old fuel in the tank. > > Many marinas don?t allow the topping up, because if you do it now, the fuel > will expand in the spring and it would leak through the vent. > > of course, your boat, your choice. > > Marek > Ottawa, ON
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