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Got this in an email. Some of it makes sense:

"I don't know what you guys are paying for gasoline...Here in California we are also paying higher, upwards of $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 where I work 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 your money.

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 the bottom.

Hope this will help you get the most value for your money."


I have known for a long time to fill up at the half way point, especially in winter to displace the air in the tank since it contains water vapor, but some of the other stuff is new to me. I hate stopping to fill up, thus I end up ignoring the tip to fill up before running low. I am going to start filling up at the halfway mark and pumping slower. Not sure the pumping speed will really make a difference or not, but it's worth a try.
 

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Great tips.
although here in Fl I'm paying 2.91
 

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"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..."


I have trouble believing this one. I mean ground temps below 1' really don't change and most tanks are 3-5' or more below ground so the temps are basically constant despite what time of day it is. Slight variations in air temp are not going to impact the temp of the soil or the UST. Now, seasonal shifts in temp..ie summer vs winter will have a small impact but still it isn't that much.

I think this guy's line of thinking applies perfectly for above ground storage tanks (AGST's) but not really for underground storage tanks (UST's).

Everything else seems to make sense from a physics point of view.
 

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so what you are saying is that the county/state weights and measures certification is incorrect? I'd think that if there is any error, it would be, at most, a couple of pennies per tank. Somebody should snopes this.

reformulated gasoline is less volatile and doesn't evaporate nearly as quickly...it also has less btu content and therefore less mpg. For those of you that still have good gas, be thankful.
 

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More info at http://www.turndownhotfuel.com/myths.html. Just checking the site. I can't answer to whether all their info is accurate. I have heard about this before. I do know in Canada they require temperature adjustments at the pumps.


Filling up your tank in the morning when it's cooler makes no difference in cost savings because the 35,000-gallon underground tanks do not dramatically change temperature in daily cycles.

- Larger fuel retailers turn over supply very rapidly, greatly reducing the fuel's time spent in the underground, insulated tanks.

- Fuel experiences significant expansion and contraction with temperature changes:


Gas = 1 percent per 15 degrees F change.
Diesel = .6 percent per 15 degrees F change.

- Canada and Hawaii have used automatic temperature adjustment devices at retail fuel pumps for a number of years.



- The Environmental Protection Agency requires gas stations to install automatic tank gauging meter systems for all underground storage tanks containing more than 10,000 gallons.

These systems incorporate fuel temperature as a factor in checking for "release detection," or tank leaks. This inventory volume information, including the fuel temperature, is recorded at the station and is used to generate regular reports to the EPA.
 

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"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 the bottom."

Not true because each dispenser above ground has its own filters. One for the regular and one for the premium.
 

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my theory is go down to empty, and fill 1/3-1/2 the tank. less gas = less weight = better mpg.
am i wrong?
 

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How much of a difference is ANY of this truly going to make in real-world practice? My guess is that most of these variables are negligible.

Is there anyone who's willing to experiment with one of these variables at a time to determine if it makes a difference in practice (like someone with VERY consistent and predictable driving habits)?

D-Rock
 

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there are so many variable that effect mpg, i dont believe youll ever be able to get a good enough control, likewise a accurate expiriment
 

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The gain/loss percentage is less than the error in measurement of your ODO and the gas pump accuracy (from rounding off etc). no way to measure it well.
 

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125ina30zone said:
my theory is go down to empty, and fill 1/3-1/2 the tank. less gas = less weight = better mpg.
am i wrong?
For some reason, I get better MPG on the first half of the tank than on the second. I go about 160 on the first half, and 100 on the 2nd.
 

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i believe thats because you can fill up way above the full line. if you know wht i mean. the half way dash isnt truely a half way level
 

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Webfur said:
125ina30zone said:
my theory is go down to empty, and fill 1/3-1/2 the tank. less gas = less weight = better mpg.
am i wrong?
For some reason, I get better MPG on the first half of the tank than on the second. I go about 160 on the first half, and 100 on the 2nd.
That's because the fuel tank shape and path the fuel float travels in isn't linear to the gauge. Your true half tank is a little above the marked half on the gauge. it isn't like the truck suddenly starts to guzzle gas because it is depressed or something. It certainly isn't heavier than it is when it is full either.
 

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125ina30zone said:
my theory is go down to empty, and fill 1/3-1/2 the tank. less gas = less weight = better mpg.
am i wrong?
generally, the lighter vehicle will move from a stop or change speed with less power req'd, but there are a lot of cases where a loaded down truck (once up to speed on the highway) will get better mpg than an empty one. This assumes no great elevation changes etc and that the tires are inflated properly for the load. The frontal section and wind resistance is the same for both trucks, but the one that weighs 1000 lbs more will/may get better mpg because it's density is greater. sort of like dropping a wiffle ball and an orange off a high drop. you know the orange will get there first because the wind against it doen't have enough force to greatly slow it down.

The reason I mention this is that I once got 22 mpg in my dad's old chevy truck that, previously had did no better than 17 or 18 on the hwy. It had 1000 lbs of crap under the camper shell that trip.
 

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I've got an SE with the Trip Computer. 2 of the settings I religiously reset with every fill-up is the Trip A (odometer) and MPG settings. I will check the indicated MPG occasionally, by dividing Trip A/Gals, and it rarely varies from the Trip Computer MPG by more than 0.5 mpg. The Trip Computer MPG indicator is pretty close I've found.

What I've also found, is that after resetting Trip A and MPG following a fill-up, it settles into a 16.8-17.0 mpg after 1/4 tank, creeps up to 17.5-18.0 mpg by 1/2 tank, and when it get's down to 1/4 tank remaining (when I usually refill), the mpg is in the 18.0-19.0 range.

I can only attribute the loss of weight for the fuel. 15 Gals x 6.3Lb/Gal = 94.5 Lbs of weight delta from 4/4, down to 1/4. 95lbs is not insignificant and might explain the approximate 1.5 mpg improvement over 3/4 tank of gas.
 
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