How much does fuel expand/contract W/Temp?

[DickWells]

Way back in 1955, when I took driver's training, our textbook said to fill up early in the morning to get cool fuel, which would expand as it warmed up in your tank. The object, of course, being to maximize your mileage.
Anybody have a feal for how much diesel expands as it warms up?
Here in Brownsville, I can't realize any benefit from pumping early in the morning, because the fuel always comes out warm from the underground tanks. It starts out cool to the touch in the handle, then the handle warms up noticeably after the first couple of quarts! Does this mean that I can expect a drop in mileage due to contraction in my tank on these cool 40 degree nights?
Just wondering. It crossed my mind the other day, when the fuel nozzle got quite warm in my hand.
DW:)

[Yukon6.2]

Hi Dick
Up here in Canada,as of mid 90's temperature compansated pumps became common.The refinery's sell their fuel at 15 degrees Celsius.So the computer has a probe in the fuel of choice,then compensating the volume to the same volume it would have at 15C.These are of course inspected and aproved by the govn't agency Wieght and Measures.Proir to these pumps some gas stations would run abunch of lines under the pavement expanding the fuel in the summer.
Basicly it's supposed to level the $$ to actual gallon or liter.
Fuel shrinks in the cold expandes in heat,so you can see how extra $$ is there in warm temps.In my case selling most of my fuel in cold temps i would be allways losing.
The pumps will allways have a decal on them if they are temperature compensated.So in the cold fill up at pumps that arn't temp compensated,and if it's warm out fill up at one's that are.
The differance is'nt big,over 14000 liters in the winter i see about 150 liter differance between my regular meter on tank farm and temp compensated meter on my truck.
It would be interesting to find out if the computer in your pickup compensates for the temp of fuel when it tells you how much fuel you are using.
Hope this helps
Thomas

[JTodd]

There are two parts to this. First, Diesel expands about 1/2 % per 15 degrees (not much) the other part is that the underground tanks are basically a constant temperature (55*, I think)

[a5150nut]

I regards to earth sheltered homes, the average temp 6 ft. under ground is 68 degrees. I had to monitor some settlement gages for some bridge abutments and the two that were mostly in sunlight during the day stayed in the 68 degree range. The one that was shaded most of the day stayed around 64 degrees. By the time we finished building the abutments the gages had 30 + feet of fill on them.

Now for expansion in the tank. I used to have a 74 3/4 ton with a 50 gallon tank in the bed. If I put in any more than 45 gallons, it would end up expanding and run out the vent tube. :D

[Hubert]

Yeah I thought the US in ground tank avg temp was like 70 or 74F. But can't remember 68F sounds ok. I'd see that as probably a regional +/- a degree or 2. I think CA tried to do something as they saw it as a way to get more taxes but not sure what happened.

Its a big ole yearly avg thing I am not sure you'll get much difference as an individual at tank fill. But for gov't or oil companies it probably makes an appreciable difference.

You also get some heat to fuel circulating back to tank so swell for sitting will be different than for driving and foam too.

I think driving class told us leave 10% tank volume for expansion with a tanker.

[a5150nut]

Been a few years since I put fuel in any heavy equipment, but, CAT used to extend the filler neck down into the tank so there would always be trapped air in the top of the tank to allow for expansion.

[DickWells]

Hm. Interesting. I never thought to read all the fine print on the pump. I just assumed that the S. Texas tanks were soaking heat, since they're burried pretty shallow under black-top.
I knew, of course, that it would mean very little to me with just a 36gal. tank, and only 20-30K miles/year. Just one of those things that enter your mind and make you want to ask.
Thanks for the come-backs.
DW:)

PS, FWIW, I'm going to get around to compiling the fuel/mileage data that's in my log for the DM from almost 3 years ago, (one of these days). Taken overall with towing and solo, it should show a fairly accurate average for an LB7, since I have kept very close track during the whole time.

[More Power]

According to a science site (http://en.allexperts.com/q/Science-Kids-3250/2008/2/volume-thermal-expansion.htm), each gallon of diesel fuel in your tank will expand 0.00046 percent for every degree increase in fuel temperature. So, 1 gallon becomes 1.04324 gallons for each degree rise in temperature.

This will produce a much bigger number when dealing with many-many thousands of gallons, like a truck stop. :eek:

Jim

[Hubert]

My brother in law told me a while back there was some hub bub on talk radio about it (taxation discussion not performance or necessarily individual economy mind you). I imagine to the oil companies it does make a pretty big difference over time.

[rustyk]

The oil terminals transfer fuel into the trucks usually compensated for temperature, and that's how stations pay for it. The dispenser (commonly referred to as the "pump") where you buy your fuel is generally not temperature compensated.

[JohnC]

a pound of fuel contains the same energy regardless of the temperature. For this reason, planes are fueled in pounds instead of gallons.

[DickWells]

Ah, that's the answer I was looking for, but didn't know how to ask for it. Reminds me of the time I asked my Vermont Top Forester neighbor about the heat potential in hard vs soft wood. He said that probably soft wood had as much or more by weight (because of the resins in it) than hard wood, but less by bulk. I kept on using both on an as-can-get basis, anyway.
DW:)

[Hubert]

I don't know much about planes but don't see the tanks being suspended on load cells to get their wieght. Then rough weather would probably screw with sensors. I suspect they measure volume and calculate weight??? The correction for altitude and temps might make a difference in the large tanks but I don't think they push the "E" on the gauge that close.

The weight unit is probably just easier to calculate loading so they can adjust thrust and angles etc easier (back in the day before computers) ????

It does sounds cooler to be hauling 10,000 lbs of fuel instead of 1400 ish gallons.

[MacDR50]

Here, by law, retail pumps are calibrated based upon a 15 degree C temperature for the fuel. In the summer the retailers make a few bucks but they lose in the winter. Some complain, some don't.

[JohnC]

... The correction for altitude and temps might make a difference in the large tanks but I don't think they push the "E" on the gauge that close.

Remember the Avianca flight that ran out of fuel and crashed on Long Island in January, 1990?

They need to know the weight of the plane, so, somehow the weight of the fuel has to be known, too, but fuel consumption is measured in pounds per hour, otherwise they'd have to continuously adjust the gallons remaining (and the value thereof...)

[rustyk]

IIRC, that flight had issues because the gages were calibrated for kg., and the fuel was delivered in lbs.

[JohnC]

The problem was that the crew was not proficient in English (the official language of air traffic control everywhere in the world) and never used the phrase "fuel emergency". The pilot has the authority to deviate from any air traffic order if he feels the safety of the flight is at stake. (He'll have to answer for it afterwards...) There were long hold times in effect that day. These guys just kept hanging out until the fires all went out.

[DickWells]

JohnC: What's the name of the fuel level sensors in planes? Having a senior moment here! Anyway, they're much more accurate than auto float senders, but MUCH more expensive. Too bad those guys kept going, knowing that the readings they must have been getting were telling them that they were going in!!! My wife put enough money in the bank for me to take lessons, back when I reached 25 years with Big Blue. I never did it, because I determined that I couldn't afford my own plane, and if I wasn't going to be able to jump into my own rig and fly anywhere, any time, then to heck with it. Bite of your nose to spite your face, I guess. Anyway, I did read some books, one written by an airliner pilot, and I remember that he said that the pilot is the final authority when it comes to the ultimate safety of the airplane. The pilot has to answer to the authorities afterwards of course, but it's better to be alive to do that.
Dick Wells:)

[moondoggie]

Good Day!

Help me out, please?

More Power says, "According to a science site (http://en.allexperts.com/q/Science-Kids-3250/2008/2/volume-thermal-expansion.htm), each gallon of diesel fuel in your tank will expand 0.00046 percent (emphasis mine) for every degree increase in fuel temperature."

The site actually says, "The thermal expansion coefficient of Diesel (in general) is 0.00046 per degree F."

These are not the same thing. I think what really happens is 1 gallon becomes 1.00046 gallon when the temp goes up 1°F.

Help!