Fuel tanks full or empty for winter?

[The_Handier_Man1]

From: photoman  (Original Message)
Sent: 9/30/2004 12:00 AM

Should the fuel tanks be full or empty for winter storage?  I have added the gas additive that extends the life of the fuel and prevents moisture, but am wondering if it's better to empty the tanks.  I have coated the insides of the tanks with POR-15.
Thanks.  Photoman



From: Sea Hag
Sent: 9/30/2004 12:19 PM

I leave just enough Stabul  treated fuel Less thatn 10 gallons in one tank to run it a few times over the winter . I drain the other tank dry .I add fresh gas in the spring to the old stuff before driving it . The fuel now days seams to go bad faster .  The original owners manual suggest leaving them full , that was written a long time ago .  I,m sure you will get other opinions , I personnally leave them empty . Sea Hag 



From: denison
Sent: 9/30/2004 2:14 PM

   Leaving the tanks empty really means there is still a puddle of fuel in the bottom of the tank, maybe a gallon or three.  When the air temp cycles up and down during the winter, the lighter hydrocarbons in the gasoline will evaporate more than the heavier ones, leaving the fuels octane slightly lower.   This happens more slowly if the tank is full enough so that the large surface area of the fuel is not available for that evaporation.  That is; if the only place air can reach the surface of the gasoline is in the filler neck, evaporation wont be so much of a factor.  It would happen even more slowly if your RV is 74 or later, as it would have had a vapor canister, and non-vented fuel caps.   I dont think evaporatin is much of a factor in a single winter anyway.
      But; in the older fuel tanks with vented caps, the thermal cycling of the night air will involve water vapor from the air condensing inside the fuel tank.   The water droplets sink to the bottom and dont leave, and a slight percentage of the water dissolves in the gasoline.   If the bottom of your fuel tank was totally sealed with a POR-15 coating, this would result in zero rust.   
     I dont worry much about it.   Since my RV is parked in the driveway all winter, the big reason to have the tanks full, is to run the genset if we lose electric power in a storm, or to refill the family car fuel tanks in case of a heavy snow.   



From: Liv42dayOK
Sent: 10/3/2004 2:19 PM

Leave it to Dave to have an RV which doubles as a mobile gas station!  His ingenuity has no limits! - Sob



From: Sea Hag
Sent: 10/8/2004 10:14 AM

Yes Daves Idea of the moblile tanker is a another Good Denison Original , I'd do the same thing if I was allowed to keep mine in my drive . esspeccially with the constant changeing price of fuel . and it would be very handy to have the genny availible for power outage to keep the furnace running and a few other small electic items . Just make sure you are fimiliar and understand elcticity and pannels if you try it . you don't want to back feed the grid . If your not good with electrical work , get someone who is to help .
   Both of my fuel tanks have drain plugs on the bottom , so when I empty the tanks there isn't much if any left in them as long as the rig is fairly level or sligtly pitched twards the drain . I agree running them out with the engine or syphon doesn't get it all out . Sea Hag