Auto-Rx Customers Questions & Answers

Frank Miller · Guru

Tips On Pumping Gas Good Info. READ AND SAVE.

Richone · Senior Member

Good info. Thanks. I guess the good news is that fuel prices are expected to drop a dime by this time next week.

benjamming · Member

not good info. Most points are not correct.

http://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=1027235#Post1027235

-- Edited by TurboJim at 16:57, 2007-11-14

TurboJim · Moderator

"Gasoline evaporates faster than you can imagine."

That post above seems to be making the rounds - I first read it on a Subaru forum. After I read the part about evaporation I was concerned that perhaps on the 1986 Jaguar XJ6 I've been working on evaporation was partly to blame for it's poor gas mileage. A XJ6 is somewhat unique in that it has two gas tanks, adding to the complexity of things.

I found two gas line fittings which I could tighten in the trunk and another four under the hood. One of these day's I'll see if I can find other loose fittings under the vehicle. The only time one smells gas is when you pop open the gas cap, and in that area everything looks as it should.

benjamming · Member

I'll post again. Much of that info is not good info. Someone else posted a rebuttal better worded than I probably could:

I have some commercial properties where I sell gas at retail, so here is my 1.99 cents on this:

Quote:"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."

Personally, I would buy whenever it is convenient for you. The tanks are so far underground, I can't imagine ambient air temperature affecting the density of the material in the tank at all.

Quote: "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."

I have a pipeline bill of lading in front of me. After correction for temperature and specific gravity, my gross load of 1994 gallons was corrected to be 1995 gallons net, that I will be billed for. It's not a big deal unless your're dealing in millions of gallons.

Quote: "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.

Our air is very clean, so we don't have vapor recovery systems mandated (yet). Nowadays, gas hardly vaporizes at all. I think this is nonsense.

Quote: "One of the most important tips is to fill up when your gas tank is HALF FUL Lor HA LF 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, herewhere I work, every truck that we load is temperature compensated so that every gallon is actually the exact amount."

Gasoline hardly evaporates at all, at least the stuff we get around here. I have never owned a UST with a floating roof and doubt there is such a thing. The above ground tanks at the pipeline terminals do have floating roofs. It's not because tthey worry about losing gas, it's because they worry about it going kaboom. What this has to do with the tank in your car, I have no idea. Buy your gas when it's convenient for you.

Frank Miller · Guru

Glad you posted thats why there is a forum. You could be right or wrong readers can take what they want and leave the rest.

benjamming · Member

neidermeyer · Member

Frank Miller wrote:

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.

***************************************

The reason for the floating roofs on the huge gasoline storage tanks is to reduce the airspace and the chance of an explosion , your car traps vapors , you don't lose fuel to evaporation ... as the writer noted gas is denser when cold AND gas is stored in underground tanks at most service stations ,,, since ground temps are stable buying fuel overnight or in early morning results in no greater density of the fuel pumped. When transporting fuel by truck where the fuel heats up slightly there is a very slight expansion of the fuel.

My rule is to buy fuel when I need it ,,, when I'm on "E" . Fuel recirculates constantly on 99%+ of modern cars with fuel injection ... many motor fuels have some small amount of alcohol (I don't believe it is required to be posted on the pump if it is 10% or less) which removes water (here in Florida humidity really does create condensation in your tank) ,, particulate contaminants get stirred up and captured by the fuel filter with the constant recirculation... therefore I see no advantage to buy at 1/2 or 1/4 tank to avoid the "dirty fuel" at the bottom of the tank ... THINK ABOUT IT ... THE FUEL PICKUP TUBE SUCKS FROM THE BOTTOM OF THE TANK ,, you're always getting the fuel off the bottom..

Oh by the way ,, high octane does not mean higher performance unless your cars owners manual says to use higher octane fuel ,, 87 octane fuel actually has more power (as measured by BTU's per gallon) than 93 octane and will give better fuel economy. If your owners manual says to use a higher octane using a lower octane will result in the computer retarding your timing and making adjustments to the cooling fan (turning on earlier) and possibly running richer to reduce combustion chamber temps and avoid preignition,, needless to say this will negatively affect your mileage.

Knightkiller · Member

I'd just like to add that I have had several fuel tanks off and apart in the last few years, off cars as old as 20+ years and all of them without fail have been SURGICALLY CLEAN inside.

I think the rubbish at the bottom of the tank is a leftover of automotive advice from our dads and granddads in the 50's!

Frank Miller · Guru

THANKS IN THESE TIMES ALL RESPONSIBLE INFO NEEDS TO BE LOOKED AT.