Some Tips from a Petroleum Industry Expert
 

Got this at work. Thought I'd share...
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Be sure to fill up your car or truck in the early morning when the ground temperature is still cold. Gas storage tanks at service stations are below ground. The colder the ground, the more dense the gasoline. As it gets warmer, gasoline expands, so buying in the afternoon or in the evening.... a gallon is not exactly a gallon. In the petroleum business, the specific gravity and the temperature of the gasoline, diesel and jet fuel, ethanol and other petroleum products plays an important role. A one-degree rise in temperature is a big deal, but the service stations don’t adjust prices at the pumps based on temperature.

Don’t squeeze the trigger of the nozzle to the fastest mode; stick to the slow mode, minimizing the vapors that are created while you’re pumping. All hoses at the pump have a vapor return. If you’re pumping on the fast rate, some of the liquid that goes to your tank becomes vapor. Those vapors are being sucked up and back into the underground storage tank so you're getting less fuel for your money.

Fill your tank when it hits the half-way mark. The more gas you have in your tank, the less air occupying its empty space. Gasoline evaporates faster than you one might think. In fact, gasoline storage tanks have an internal floating roof. This roof serves as zero clearance between the gas and the atmosphere, so it minimizes the evaporation.


Finally, if there is a gasoline truck pumping in to the storage tanks when you stop to buy gas, DO NOT fill up. The gasoline may be stirring up dirt that normally settles at the bottom.
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Good advice but how much are you actually saving in real numbers. I think it would equal a marginal amount for an average driver. A trucker though could see a nice savings.

How come at the pump it says "Volume is corrected to 15 degrees Celsius"?

is it always 15 degrees there? Then how can that be true.

The tanks underground hold alot of fuel. Being underground it is also very well insulated from outside temperature changes. This means that the contents of the tank won't change as much in temperature compared to if the tank were above ground. It also takes a while to change temperature of a large volume of liquid. The fuel will not appreciably change temperature between day and night as a result. Not saying it won't change temperature. If it only changes 4 or 5 degrees or so, is the volume difference really going to be appreciable? No.

The only one of these suggestions I would agree with is the last one. The others are BS (in my opinion).

It wouldn't be too hard to imagine the storage tanks being cooled/heated to that temp...

when you average 12mpg it could make a difference too...sigh i need to get rid of my lead foot.

Seems around here, they only fill up the tanks at night. Therefore filling up in the morning,, i'm gonna get the stuff that's stirred up?

Total BS.

The pumps at stations meter the same no matter what the temp of the petrol in the ground is. The vapor return is just that a vapor return which has nothing what so ever to do with amount of liquid volume that is metered out of the pump. As far as the liquid getting sucked back up as vapor that is so far off, the system is designed to stop that, that is why when it gets liquid returning as vapor it shuts off clicking the handle. Now you can cheat yourself if you get one of those handles that keep tripping off and you are doing the squeeze trip dance with it.
On a fill up you could possible lose a whole 10th of a gallon or so.

This is just another internet hoax email that is meaningless.

The one about stirring up the bottom has some merit, the rest is absolute folklore, from someone who knows NOTHING about the subject.

.....and Mr. Alksmoke has also posted this before, knock it off.

S

Actually... that one has the least amount of merit it to it, for 3 reasons:

1) the storage tank exit pipes (where the fuel gets sucked from) go to the bottom of the tank...where all the crud would be, if it even exists in the first place...which it doesn't in large quantities...

2) Pumps have nice little filters on them, so the garbage that does happen to get sucked through gets trapped in the filters.

3) If you think it's any less turbulant with pipes sucking fuel out verses pipes dumping fuel in, you're sadly mistaken.

ouch.. even during drag race or autocross days, I don't think I've ever gotten a tank that bad....

and I'm boosted.

As someone who is in the "Petroleum Industry", I have to 2nd rotary's comments also. This is just another intarweb email FW: that someone wrote trying to come off as being clever. In fact, if an argument can even be made regarding time of day to buy gas, I would say that I'd be paying attention to the time of day that the gas was *delivered*, rather than the time of day I'm actually buying it. Because gas inside the delivery truck is certainly more affected by ambient temps, than gas that's already inside the storage tank.
But the combined effects of multiple deliveries & comingled batches inside the station's storage tank, means that differences are insignificant for practical purposes.

mythbusters