Dunno mate, all i can say is it's always bloody freezing where i live and it still costs me about £10 for 90 miles worth of petrol!

Here in Canada the pumps all carry signage that volume measurment is adjusted to a certain fixed temperature (23C I think).

All matter expands and contracts with temperature. The gas is probably more dense in winter compared to summer but I'm not sure how big daily temperature variations affect this (short timespan compared to seasons), especially with the tanks underground.
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don't think it is weather related, from what my local media has been broadcasting, gas prices are raised locally at gas stations generally between the hours of 9-10am and 2-3pm, so if there is any flucuation in prices, I guess the night would be the best time to buy since you know the price will be stable till the next morning...but seriously I don't know..just speculating..

I can see how the lower temperature might make a minor difference, but what are we talking about here, a few milliliters at most I would think. But hey, a penny here a penny there...

Pumping at dawn and dusk does indeed give you more 'money for your oil'. It is due to evapouration. Gas has a low evapouration point, so the cooler it is when you pump, the better. Less gas that you pump will evapourate, thus you are "getting more for your money". Learned this in Drivers Ed a few weeks ago.

Slightly over inflate your tires will save you 2-3 miles per gallon.

Be amazed how many have low tire pressure and that is one of the simplest thinks to correct.

Convert to propane is another, which is all I use...$1.59/gallon

Wait... you can covert from gas to propane? How do you do that?

I think the evaporation theory is correct. I hear commercials on the radio all the time that give ideas to cut down on pollution. Ride sharing, tune-ups and pumping gas before sunrise or later at night is always mentioned.

Either way it will expand the next day and evaporate out the vent.

Either way it will expand the next day and evaporate out the vent.

From memory there was a uni study that established that filling up your tank on a hot windy day would cause a few percent loss out of the tank. So it they advised fillup when there was no wind and when the temprature was cooler ie first thing in the morning. In Australia I run my van on what we call LPG which is similiar to your propane. It costs about $2000 to convert but the savings are great in my business. Apparently it causes less wear in the engine and it is a lot better for the environment than petrol!!! There is a small loss in power.

However if you really want to save money get a pushbike

maybe I'll pump at night then lol Dcfusion is that Eiki Yuri from "Gravatation"

So I guess you do get a little more for you money when pumping gas at night. The main reason I was curious is because there is a reasonably priced gas station just down the street so it is no big deal to go there at night, and if I can get just a little bit more for my dollar, why not?

Lamagraa - no, it's not Eiki Yuri, it's one of the characters from 'Angel Sanctuary", can't recall the character's name, though.

I would say early in the morning to take advantage of all the nightly cooling effect. Once the sun has set, the ambient temp and humidity still takes several hours to adjust. The old saying goes its always darkest just before dawn also relates to temperature as well. Its most always the coldest just before sun-up. I usually get my fuel at around 7:30 am. I have noticed it takes less to fill up. Not much less but less nevertheless.

Myth: Buying your gasoline in the early morning or in the evening when it is cooler outside will save you money. Gas is moderately denser in cold temperatures. Proponents of this money-saver say that because gas pumps measure fuel volume rather than density, you'll get more for your money if you buy fuel when it is cool outside.

Truth: "You're not going to see much difference if you fill up on a 50-degree day or if you fill up on an 80-degree day," Baxter says.

That's because filling stations keep gas underground, where the temperature is fairly stable.

Assuming gas may be slightly denser in the early morning or evening, if you fill up during those times, you might get about 1/30 of a pint more - about 0.0041667 of a gallon.

Many people fuel up on their way to or from work, so you could end up spending more time in line, idling your engine as you wait - and wasting gasoline.

/ap4qp

Maybe save a penny if you fillup at 5am....

Regemacher beat me to it -- it's an urban legend with a SLIGHT basis in fact.

As several are pointing out, the "savings" amounts to pennies over the course of a month or more. You can do more to cut gas costs by limiting trips, shopping for stations with the best prices, and paying attention to tire pressure.