infidel

You are correct, a bad choice of terms, should have said pressurizeing.

dspencer

I doubt seriously that 30 degree pump temperature would account for ANY measureable mileage or volume differences. I am no scientist but liquids do not expand or contract appreciably at those temperature differences. If so, my fuel tank would have to be made with more venting or it would expand or contract like an accordian(sp) as fuel temperatures vary much more during normal running.
Also, if the volumes at different temperatures accounted for anywhere near the differences mentioned (10mpg Flying J compared to 12.5 mpg elsewhere) I am sure the government would have set temperature standards for fuel delivery or any SMART distribution point would heat its fuel the same.

If there is or was a difference in mpg one station vs another I would check fuel quality (cetane) rather than temperature.

RickG

It is likely additives rather than heated tanks that cause the difference in temperature . This could also cause the fuel to have lower BTU's and be less efficient .

Gear Poet

Ya, that's what I was getting at in an earlier post.

Tom Bolitho

What you are actually talking about is fuel density. Temperature has a large affect on diesel fuel. When you figure the amount of BTU's in a gallon of fuel at 50 degrees and the number in a gallon at 80 degrees there is a big difference. I have problems at work because our fuelman will top off the trucks at night when it is cool. If the truck isn't used the next day it will puke fuel out of the tank from expansion.

JohnnyH

Just an example of density vs volume on a larger scale. I fly an airplane that has a fuel capacity of 29500 lbs or 4402 US gallons based on 6.7 lbs per gallon of Jet A. When we top off in the winter we are able to put 30000 lbs in the tanks. When we top off in the summer we can only get about 29300 lbs. Our fuel gague indicates in lbs, not gallons. The same volume of fuel is going in, it just weighs less and yeilds less BTU's. Considering the fact that our truck tanks are about 1/1000 the size of what I'm comparing to, the diffrence would be negligable. JMO

Tom Bolitho

Using JohnnyH's figures on his airplane When used in our trucks at 15 mpg works out to about a 1/3 of a mile more per gallon.

P Kennedy

The one important factor eveybody has left out is were the fuel stops above ground or below ground tank storage, there is no way above ground storage will remain as cool as the tanks 8' below the surface of the ground. Also any diesel engine all of which return fuel to the tank are going to experience the same problem, as you drive pumping cool fuel through the engine it is going to get warmer. Pulling hard down the highway it will gain heat even quicker depending on the outside air temperature and the lowest temperature of the material it is pumped through( the engine). Detroit Diesel had some serious heat issues with the earlier DDEC motors boiling the fuel on hot days pulling in the hills or into the wind. 180-200F fuel temps are normal on summer days in highway tractors and that is why we have higher density fuel in the summer than in the winter. As far as reduced fuel milage experiment, one would have to include the same vehicle, load, outside temp, air density, A/C on or off and driver to accurately compare. I would almost bet that Flying J fuel would have certain additives and be processed at a different refinery to be able to generate such discrepancies in milages with common factors. Filling your tank in the morning with cool fuel is an old trick and it works but more important is the way we fill our tanks for consistant fuel milage numbers. The Dodge is notorius for air pockets and foam when filling near the top of the tank, if you have the patience to fill until the filler neck has visible liquid fuel not foam every time your milage records will be more consistantly accurate. Geographical location is a major factor in where the fuel is supplied from some centers only have one refinery supplying the entire area. There are times where the name on the sign makes no difference other than additives because all the fuel comes from one supplier. PK

Lightman

Pkennedy, that is the case most of the time. Almost all cities share the same diesel under different brands, as it all travels down shared pipelines to the terminals, at which point it's branded and additized if that brand chooses to, and put in trucks.

Haulin_in_Dixie

Now this may sound crazy, but I have always gotten better fuel mileage on Atlanta based fuel than Birmingham based fuel.

newriverSpecon

I've been told the same about gas. However I did a 20,000 mile test on a Cherokee I bought new in 2000. The first 10,000 I ran Dimond Shamrock 99.9%. The remainder was Texaco and a few Cheveron. I happen to run Cheveron for a few tanks and saw 2 mpg increase. My Brother-in-law had a 78 f-250 w/460 (not hi-po). It would pinning on anything but Cheveron.

I am not in the gas/fuel busines and do not know the details of delivery or additives at whatever stages, but I know the results I found. I know what gasoline I use in my bike and the car before we traded it. I tracked every tank of gas and every mile.

I have been chasing a couple of MPG loss over the last year in my truck. I realized after reading this thread it was very close to the time I started useing F.J. due to ease of access compared to the other options. I will begin testing this theroy on my next fill up and have preliminary results with in two weeks.


Randy

moterhead

Why would you suck up more contaminants and water with a low fuel level than with a higher one? The fuel pickup is at a fixed location in the tank. It always sucks from the same spot at the bottom of the tank. Doesn't float up and down like your fuel guage arm does. Please explain.

Haulin_in_Dixie

I don't pay much attention to this on my truck but here is why. The engine constantly returns fuel heated by the head where the return channels run. The lower the fuel in the tank, the higher the temperature of the fuel. The engine is 180 or so degrees and the fuel is the same temperature when injected into the tank.

I have been thinking of a trans temperature gage in the fuel line to find out the real scoop on fuel temperature.

I have my own thoughts on the contaminate thing. I learned from the big trucks that you don't want the garbage to collect in the tank, better to get it out as it comes in. A good filter system takes care of it. Allowed to build up and you have a problem when it finally hits the pickup. Mine is bottom feed, trash goes out first. Never have had a drop of wather from the seperator and the filters last great length. When I openied up my tank to install the bottom feed, the tank was spotless after 200k or so.

Tom Bolitho

Why would you suck up the more water and contaminates from a low tank?
Because the same amount of junk in the tank falls out of suspension as the fuel is used. The fuel is more contaminated % wise on a low tank than full. Better odds of getting a really lousey suck off of the bottom mixture.

Haulin_in_Dixie

Ok Tankeryanker should be able to answer this. Is number 1 fuel cheaper than number 2? If it is ok to do it in winter, bet they could be doing it in summer.