I got this e-mailed to me the other day, and I was gonna reply to my buddy with the knowledge I have about specific gravity in racing fuels and how it makes a difference in mixing pop, but I didn't know if it was the same for regular grades of gasoline... Check this out and chime in- somewhere along the line I can't see there being that much of a difference, but maybe I'm wrong- I know a few degrees can really hose you at fuel check if you cut too close..

TIPS ON PUMPING GAS (Good information)
I don't know what you guys are paying for gasoline.... but here in California we are also paying higher, up to $3.50 per gallon. But my line of work is in petroleum for about 31 years now, so here are some tricks to get more of your money's worth for every gallon..

Here at the Kinder Morgan Pipeline in San Jose , CA we deliver about 4 million gallons in a 24-hour period thru the pipeline. One day is diesel the next day is jet fuel, and gasoline, regular and premium grades. We have 34-storage tanks here with a total capacity of 16,800,000 gallons.

Only buy or fill up your car or truck in the early morning when the ground temperature is still cold. Remember that all service stations have their storage tanks buried below ground. The colder the ground the more dense the gasoline, when it gets warmer gasoline expands, so buying in the afternoon or in the evening....your 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 1-degree rise in temperature is a big deal for this business. But the service stations do not have temperature compensation at the pumps.

When you're filling up do not squeeze the trigger of the nozzle to a fast mode . If you look you will see that the trigger has three (3) stages: low, middle, and high. In slow mode you should be pumping on low speed, thereby minimizing the vapors that are created while you are pumping. All hoses at the pump have a vapor return. If you are 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 worth for you r mon ey.

One of the most important tips is to fill up when your gas tank is HALF
FULL or HALF EMPTY. The reason for this is, the more gas you have in your tank the less air occupying its empty space. Gasoline evaporates faster than you can imagine. 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. Unlike service stations, here where I work, every truck that we load is temperature compensated so that every gallon is actually the exact amount.

Another reminder, if there is a gasoline truck pumping into the storage tanks when you stop to buy gas, DO NOT fill up--most likely the gasoline is being stirred up as the gas is being delivered, and you might pick up some of the dirt that normally settles on th e bottom.
Hope this will help you get the most value for your money.

DO SHARE THESE TIPS WITH OTHERS!

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Thanks for the tip Martin. I'll certainly give it a try!

interesting - thanks.

Here is a link to an article that may help. What I get out of it is

1.) Gasoline pumps are thermally compensating and

2.) It really makes no difference when you fill up

Flow Meter Tutorial

Part 3 is a good place to start

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I am far from an expert on this, but here's my take on filling up in the morning/afternoon. Underground temperature doesn't change much from morning to evening, it only changes from season to season. Because we are on a public water system, in the winter our water temperature is around 50 degrees all of the time. In the summer, the water temperature goes up to around 70 degrees or so, all of the time. If there is a time to buy gas, I would have to guess that it would be in the winter rather than the summer.

But that's just my opinion, I could be wrong.

Murdock.

I'm sorry but this all smells of urban myth.

This is hooey. As another person noted, the ground temperature is quite stable -- that's why people have geothermal heating/cooling systems. It varies month-to-month, not hour to hour.

While you're at it, go into the store, take a leak, buy a pack of smokes and otherwise inconvenience everyone else waiting to use the pump, so that you can save $0.02 on your total gas purchase.

The science here is just bad. The evaporation is caused by the amount of gas exposed to the surface (read the stuff about the floating roof), not by the amount of gas in the tank. Imagine a glass 3/4 full, 1/2 full, and 1/4 full. They all have the exact same surface exposed to the air. And driving around with a full tank of gas weighs more, and certainly reduces your gas mileage by at least what this "tip" would save you.

OK, that one I'll buy.

I'll have to agree on the thing about temp being complete hooey.

The temperature below ground after you get beneath the frost line (whatever that is for your area) is CONSTANT year-round. Winter, spring, summer, or fall....it's all the same. Ever been in a cave? Same temp, always.

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I agree completely.

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John

I agree. The first clue should have been "I got this emailed to me".

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Snopes breaks it down..

Urban Legends Reference Pages: Tips on Pumping Gas

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OK here's my take on it.(I have been driving a gasoline tanker for 28 years)
#1)Ground temp.- we get a inventory print out before we make a delivery to verify it will hold the gals we have loaded.For some odd reason I always look at the temp,it does not very much,the tanks are buried an average of 100+" deep(pretty constant ground temp)
2)pulling the trigger to slow mode- I don't know but won't you get the same amount of vapors from a gallon of gas if you pump it slow as compared to fast? and if you got it on the first notch you're going to have a WHOLE bunch of ticked off people as stated in an earlier post.
3)pumping when the tanker is there-Well that's kind of a depends deal.If it's a high volume(always busy) station it's not going to be a problem. due to some rather strict environmental laws most tanks have been replaced within a couple of years anyway & do not have years of sludge built up in them.Besides, modern gasoline pumps have 10 micron filters on them that also stop water.

If you pump in the slow mode, aren't you standing there longer with your gas cap off?

Driving my own semi-truck and getting 7 MPG on a good week, I've adopted some driving habits that I know save me fuel and wear and tear over the years. One is that I rarely stop for traffic lights, even in my car. I paid for the energy to get my vehicle moving and I don't want to use braking energy to throw that away just to have to spend it all over to get moving again. I look ahead and watch which traffic is doing what to have an idea when the light's going to turn green for me and, what slowing I have to do is done ahead of time. I usually cross an intersection just as I'm achieving the following distance behind the next vehicle that I want.

Most drivers will do like everyone else and just run right up to the next vehicle and stop. If they're enough spaces back, the time it takes them to get going again can also cost them another red light. I can take a heavy, loaded truck and make better time than most drivers can empty.

Same in stop and go traffic except, I don't stop and go. I look ahead and leave a LOT of following distance. Traffic usually moves like one big slinky (what we played with when not playing with sticks in the 70s. Google it.). I time it so that I drive the average speed that the traffic is moving at.

I was just at a safety meeting in Georgia that's a requirement of the company I'm leased to due to a three year anniversary with them. Some of the other drivers were in the same meeting as new hires or as a required six month follow up. When we were chatting and I told them about the above driving tip, they didn't believe me, as many don't. They said "People will just cut in front of you and fill in the gap." Believe it or not, if you leave enough space, most people won't do it. The ones who do usually aren't there long. They tried to say "Not where I drive." When I told them I go to the northeast and back every week, that argument got shut up quickly.

People don't want what's easy. If you leave a lot of following distance, they think there must be something wrong with that lane. They look a lot like they're thinking about it but, they don't do it. When they figure out that they should have as I'm zooming by, they can't because they stopped too close to the car in front of them to leave room to come around! If you rush up and try to close the distance up, they'll start coming over. You'd have to try this to believe me. Even if I lose a few spaces, that doesn't cost me what stopping and starting over and over would. What am I losing when traffic's moving again if you divide it out? A few seconds? Compared to more fuel, more wear and tear, and more work working a clutch pedal?

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