Do you think its true about gasoline?????

Question

I got a forward about gasoline that says to fill up in the morning when its cool outside and to pump slowly anf fill it to the top because the gasoline is denser when its cold outside and you will get more for your money and that gas stations depend on the percentage they make when its hot outside. I have been doing this because gas prices are soooo high here and honestly, I think it is WORKING!!! It really seems like the gas gauge is not going down nearly as fast!!! Could there be a real basis for this???

Answer 1

Yes, gas expands when it's hot and contracts when it's cool so a gallon at a lower temp. will have a bit more bang for the buck.  This is why airplanes measure fuel loads in pounds.  Hot or cold, a pound is a pound.  

Is the difference enough to make a real difference with a car?  I wouldn't have thought so (just a few gallons in a car) but maybe...  Anyway it can't hurt.  I don't know what good pumping slowly will do though.

Answer 2

The tiny amount of gas you would get extra is hardly noticeable. Also, the small amount of gas lost to vapor when filling is negligible. The thing about not filling when they're refilling the tanks from a tanker truck is true, you might get some more sediment and c**p that would be stirred up when filling.

Answer 3

Hi!

It's in the Internet so it must be true, see part way down in the link below.

One mistake though: don't fill the tank right up, stop it after the first "click". If  you fill right to the top, then when the gas warms up in your tank, it expands and leaks onto the ground and vents into the atmosphere: you lose the benefit of your early morning fill, and you pollute the air too.

Answer 4

Yes, the pumps measure the liquid content.

Cooler liquids are more dense.

You will get slightly more fuel if you fill-up at the cooler time  of day.

This fuel density of fuel is why aircraft measure their fuel in pounds not gallons.

Answer 5

that is cost alot?

Answer 6

The theories behind the email are correct,  the facts may not be.

Gasoline is denser when it is cool (specific gravity),  but  it depends on the temperature of the underground storage tank  and the temperature of the last fuel dropped.    The outside temperature doesn't matter that much except for what is in your car.    As the day warms,  the gas in your tank will expand slightly.

Filling your tank slowly helps limit the amount of gas already measured into your  car that will turn into vapor.    Not running the tank much below half limits the amount of vapor that can be in your tank to be forced back into the vapor recovery system as you fill.  

More than anything else,   your driving habits can save fuel.   Slowing down is the most important,  looking far ahead and planning to allow you to maintain a steady speed comes next.   This means no tailgating,  looking at the traffic as far ahead as you can see,   timing the lights so you don't have to stop.......

Answer 7

Here's something to think about. Gasoline tanks are buried several feet undergroound. The temperature is extremely stable. The temperature of the fuel in these tanks doesn't fluctuate overnight. If this actually worked, and it was documented anywhere other than chain emails and internet legends, you would see thousands of people lined up at gas stations every morning and no one at any other time. People have a tendency to believe this kind of thing because there is just enough truth to them and a whole lot of embellishment. It is true that gasoline expands as it is heated, but the reality is that it is stored at such a constant temperature that it is not a factor. The biggest things that affect your fuel economy are the driving techniques you use. The biggest improvements in your fuel economy will be found with improving these techniques, such as tire inflation, driving with a gentle touch on the gas pedal, using your A/C only when needed, routine maintainance, staying out of stop and go traffic, cleaning out the car of extra weight, driving a constant speed, not speeding, not tailgating, and a million other common-sense tips that are readily available in print and on the web.

Answer 8

You think about the price of gas at one station and a dime higher at another station. 15 gallons of gas is only a buck fifty difference, but the perception of the extra dime makes you cringe as if the price would be double. The same is true about filling up when it is cool vs hot/ bla bla bla.  Your looking at maybe a tenth of a gallon in savings overall, if that much. Just for grins take 2 one gallon gas jugs fill one up at noon full speed. take the 2ND and fill it up in the freezing cold morning hours real slow. Both one gallon exactly.  The end result would be one gallon of gas at the same price. Then take both gas jugs and weigh them. I bet there would not be more than 1 once difference.

Answer 9

it slightly affects it but not any amount that you would really notice

there was a news report on it the other day

Answer 10

I doubt that in a 25 gallon tank it would make much difference,but the gas will already be cool no matter the outside temp from being in an underground tank.I work at Toledo Jeep Wrangler Assembly plant and the gas is cooled by refrigeration to 30-40 degrees to make it pump faster..

Answer 11

It's more prevalent to say gasoline is more dense when the ground temperature is coldest. (Probably at 6 or so in the morning) It depends on where you live. (first link) Arizona and Florida has it worst.

If you buy 20 gallons at 82 degree gasoline temperature at $3.50 a gallon you end up losing $1.06 in energy. (second link)

This is not counting the temperature rise between the 82 degree underground tank temp and the final temperature when going through the pump.

Alternatively, if you buy 20 gallons at 47 degree gas temp (Alaska) at $3.50 a gallon you will save $0.63.

Answer 12

One aspect not covered by this is the size of your fuel tank.  If the tank is metal, the capacity will change as the metal expands and contracts with the temperature.

I read the same thing lately and it falls into the urban myth category.  Drive smoother, drive a little slower, and combine trips where possible.  Change the air filter.  Air up the tires to 35 psi.  YOU as the driver have a greater effect on gas mileage than waiting to fill up on a cool morning.

Answer 13

Well maybe, gasoline has an extremly low freezing point so I dont think the weather out side affecting it too much. MAYBE it might afect the gas tank because the cold shrinks metal and the hot expands it. But hey if you think it works that's all it matters, maybe it does. So keep doing it, it will keep your mind at ease.

Answer 14

what you are saying is technicaly correct, but the problem lies with the fact that the storage tanks are buried deap in the ground and it would take quite a while for the heat to reach them to expand the fuel.

but if you are experiencing what you say you are then carry on, but getting more milage out of your tank, that is the myth, that is governed by your cars computer or carby, there are other factors involved, but higher milage on colder fuel, Naaahhh :o)

Answer 15

No, no, no, no. This is a myth perpetuated by idiots in the media who don't understand chemistry and physics.

Gasoline is stored in underground tanks where the temperature rarely varies more than a tenth of one degree during the course of a day. Gasoline is drawn out of the tanks by pumps and travels to your car in less than 5 seconds after leaving the ground. There is no temperature dependent benefit to buying gasoline at any particular time of the day.

Beyond this rumor, gasoline has energy based on the number of molecules, not the volume of gasoline. If your car's fuel is very warm or very cold, your engine's computer will adjust fuel flow to compensate for the varying density of product. As gasoline warms up, it will have less energy per given volume and your car will inject more with each cycle. When it cools down, your car will inject less gasoline, since it's getting the energy it needs from a lower volume.

Answer 16

The only thing that is true is the part about filling your gas tank slowly, I do that. I just took a trip to Los Angeles from San Francisco and I got 41 MPG. My gas tank is only 11.1galones.

Each way used less than a full tank of gas (around 3/4 tank).

Want I did the day before I left was got an oil change, wheel alignment, tire rotation, and a new engine air filter; I do all this as needed or according to the owners manual.

Answer 17

Yes it is true...

Answer 18

It probably has scientific support but the phyciatrist has more relevance here.

I've seen the obsession grip people before where they queue for a long time to save cents on their fill up, and doing u turns etc to get to the favourable station and pump outlet.

Compare the time and emotional upset to secure this minimal saving against the "hassle" of it all..it doesn't add up.

Better still to avoid the offending outlets completely and they'll go out of business......not true unfortunately but point will be noted.

Answer 19

No it's not true, and you're seeing a placebo effect.

Though it might be good to not fill up in the morning because that's typically when prices get raised to s***w the morning commute.