Fill up in the morning? Myth busted, plausible, confirmed?

[JanGeo]

Guys! come on, unless your station has the fillers in a hole where rain water collects, the fuel is going to be clean - the amount of fuel being pumped through a tank is so large that the chances of there being anything but gas in there is infinitesimal. Any water will be absorbed by the ethanol and in fact the fuel should contain less moisture than that which was in the tank for the past week since it is fresh. You are actually better off with a load of fresh gas since it is cleaner and the sediment (if any) hasn't had a chance to build up and concentrate towards the bottom of the tank near the outlet as the tank level gets low. Besides what are the chances of you getting fuel JUST AFTER the truck filled it up.

[Jay2TheRescue]

I have seen stations where rain water would fill the holes where the tank fill holes were, but all stations have water in the tanks, its just a question of how much. Condensation forms when fuel is pumped out of the tank it is replaced by air. This air has water in it. When it cools the water condenses on the walls of the tank and falls to the bottom. I have never seen an underground tank that didn't have some amount of water in it.

[JanGeo]

That said then the ethanol gas blend in a near empty tank would probably be saturated if there was standing water in the bottom of the tank. Ok then your arguement for it getting mixed up upon filling is somewhat valid but also 1000-2000 gallons of fresh gas with 10% dry ethanol would soak up a lot of that water when mixed into the tank. Although water in the fuel can cause corrosion it can also aid in combustion like water injection.

[Jay2TheRescue]

When I worked for 7-11 in college we sold E-10, and I know there were no leaks because I checked the tanks nightly and did the fuel reports myself. Our tanks normally had 2 -3 inches of water in the bottom of the tanks. Same when I worked for a fuel station operated by the USMC. No leaks, but there were always a few inches of water in the bottom of the tank.

I just don't like the idea of water in my tank. At the very least any water pumped into your tank has displaced gasoline, and you paid $2/gal for water.

-Jay

[trollbait]

You are assuming the ethanol is dry to begin with. It takes more than basic distillation to get absolute ethanol, and even then, it will gather moisture from the air if not stored properly.

Do they start with absolute ethanol for auto fuel? Or is the trace benzene big enough deal not to?

[JanGeo]

From what I have read about the ethanol process they get it pretty dry with a final stage to absorb most of the water out of it.

From what Jay is saying I guess I better not be gassing up after they fill the tanks - hard to believe that much water would be there but then again that is the problem with vented tanks. You would think they would have some way of constantly draining that water out from the bottom of the tank. Makes me wonder if the initial increase of MPG with acetone was from the water in my gas tank being absorbed into the fuel and burnt as a combustion enhancement.

http://en.wikipedia.org/wiki/Ethanol_fuel
Wiki had this way down on the page . . .

"With increasing attention being paid to saving energy, many methods have been proposed that avoid distillation all together for dehydration. Of these methods, a third method has emerged and has been adopted by the majority of modern ethanol plants. This new process uses molecular sieves to remove water from fuel ethanol. In this process, ethanol vapor under pressure passes through a bed of molecular sieve beads. The bead's pores are sized to allow absorption of water while excluding ethanol. After a period of time, the bed is regenerated under vacuum to remove the absorbed water. Two beds are used so that one is available to absorb water while the other is being regenerated. This dehydration technology can account for energy saving of 3,000 btus/gallon compared to earlier azeotropic distillation."

[Jay2TheRescue]

The problem is you just can't drain it off. Water that has been in contact with gasoline is considered hazzardous itself. We had to have it professionally pumped out and sealed in 55 gallon drums to be hauled off by a disposal company.

[shatto]

I suspect this is being done because their attorneys recommended being proactive because some jerk will try getting some money from a lawsuit.

Costco sells a huge volume of gasoline. My store sells at least 30,000 gallons a day. Sometimes there are two delivery trucks there at the same time.

This translates to all the fuel being at pretty much the same temperature and I don't imagine that much cooling takes place the nine hours the station is closed.

[101mpg]

With YEARS of data I can tell you conclusively it is NOT a myth. You need to have big differences in temperature, however. If you live in the desert, Southern California, or other places where it gets pretty hot and the daily temperature variance can be 30-40+ degrees, it is TOTALLY true. It is NOT a myth.

Filling up at a station where they have just pumped in gas and it has not had time to settle WILL put crap into your tank. Sediment gets stirred up, it goes into your gas. You think they filter down to one micron? Hardly. More like a colander trying to catch sand - which doesn't really work.

Winter months, days with much less temperature variance - this will not show much if any difference in MPG, but large temperature variance over the day WILL show better results if you fill up in the morning. 6 am is best in the summer. Myth CONFIRMED. Anyone who says otherwise hasn't checked with the right variables.

The reason the US companies have not gone to temperature adjusted pumps is because it makes no monetary sense for them to do so. More customers in daylight hours with expanded gasoline, more money. Why would they do so voluntarily? Most won't, and only will do so if forced.

[VetteOwner]

i dunno about my area (maybe changed 20 degrees from daytime to night temp)

but i had to fill up 15 gallons and after it was done the pump nozzle was ice cold when it was 70F out (i filled up at 5pm too)

so for my area i really dont think it makes a whole lotta difference....(that and our stations have those huge pavilion so you and the pumps are always in the shade)