The Great Gasoline Tank Mystery!

[Jtels2593]

Hey all,

The Camaro has a 16.8 gallon fuel tank according to the capacity specs, correct? After replacing my oxygen sensors, I managed to boost my fuel economy from 22-23 mpg to around 27-28 mpg. 90% of my driving is all highway.

Here is whats going on.. I am getting 27 mpg out of a 16.8 gallon fuel tank which means I should travel 453.6 miles (give or take) on a full tank of gasoline. The problem is that I have only been traveling approximately 300 miles (give or take) on what the gasoline guage says is a full tank of gas. I tested this twice and both occasions I drove the car until the warning light came on. I stopped at the fuel station to fill up and only pumped between 11 and 12 gallons of gasoline into the car. 12 gallons multiplied by 27 mpg equals 324 miles. So even though my warning light comes on, I should have anywhere between 4-5 gallons of gasoline left in the tank according to my math.

I am not quite sure what the problem is. I have the paperwork from the previous owner who had a new fuel pump and sending unit installed on 8/26/09 with 99,641 miles on the OD. The car now has just over 110k miles on the clock. Either my math is fuzzy or something is wrong.

Has anyone else ever experienced this problem?

[cam98aro]

Re: The Great Gasoline Tank Mystery!

a 2000 camaro has a 16.8 gallon tank

when you fill up the tank, it does NOT fill up all of the way, the tank will only hold 16.8 gallons if you basically force it to.

when you are driving, you are not completely emptying your tank.

go to the gas station, write down your mileage when you fill up. drive the car until you need more gas, then when you pull up, write your mileage down again, and write how many gallons of gas you put in. divide that by how many miles you have driven, and you will get your true mpg.

im not really seeing a problem with your situation though, so i cant help you there. gas tanks never go completely empty, and when mine is below empty i can usually pump 13.5 gal on a 15.5 tank

[Bandit127]

Re: The Great Gasoline Tank Mystery!

The most I've ever put in was 14.5 gallons, and thats in a 94 3.4, at which point I coasted to the gas station because it was literally unable to even idle. (I know, thats a big no no).

I "think" the light comes on with 4-5 gallons left in for two reasons: Keeps a healthy amount of distance the car can go and to prevent overheating a fuel pump via dry pumping. Pumping, not humping.

[Jtels2593]

Re: The Great Gasoline Tank Mystery!

I average out my mileage by both the trip odometer and the method that you explained and it usually averages out the same. Regarding your statements about the fuel tank not holding 16.8 gallons unless forced, and a couple of gallons left in the tank once the warning light comes on.. the math somewhat adds up.

It was nice when gasoline was cheap a few years ago and I didn't constantly care or worry about fuel mileage.

[debord97]

Re: The Great Gasoline Tank Mystery!

back when i had my new mustang I noticed I would get 50 miles less to the tank in the winter than I would in the summer. I talked to a guy that works for sanford gas here in texas and he told me they had different mixtures for summer and winter. dont know how true that is but it would explain a few things. most people do less traveling in the winter using less gas. so, the winter mixture burns faster making you use more fuel.
like i said dont know if any of it is true but thats what the guy told me.

[T-Mill]

Re: The Great Gasoline Tank Mystery!

from what I recall... there aren't different mixtures, but since the gas expands and contracts with temperature like most everything else... The same volume of gasoline won't necessarily equal the same mass of gasoline depending on temperature... some stations compensate their pumps for this and some don't

[vanbibber]

Re: The Great Gasoline Tank Mystery!

from what I recall... there aren't different mixtures, but since the gas expands and contracts with temperature like most everything else... The same volume of gasoline won't necessarily equal the same mass of gasoline depending on temperature... some stations compensate their pumps for this and some don't

yup, hence why its better to fill your car up early in the morning opposed to midday to get that little extra.

[Bird_Of_Prey]

Re: The Great Gasoline Tank Mystery!

from what I recall... there aren't different mixtures, but since the gas expands and contracts with temperature like most everything else... The same volume of gasoline won't necessarily equal the same mass of gasoline depending on temperature... some stations compensate their pumps for this and some don't

Oh, there are many different mixtures. Summer blend, winter blend, E10, all kinds of stuff. Don't be so quick to discount that from happening.

[cam98aro]

Re: The Great Gasoline Tank Mystery!

from what I recall... there aren't different mixtures, but since the gas expands and contracts with temperature like most everything else... The same volume of gasoline won't necessarily equal the same mass of gasoline depending on temperature... some stations compensate their pumps for this and some don't

there are, IIRC summer fuel doesnt evaporate as much as the winter stuff does, it can also vary between gas stations.

i can tell the difference in how my car runs with different gas stations i get gas at, the idle quality is very dramatic

[Rob Bell]

Re: The Great Gasoline Tank Mystery!

On my 2002, I can get at least 50 miles once the warning light comes on. I won't push it past that though, since I don't want to walk. But I can usually cram over 15 gallons in there if I let it really run low.

There is a big difference between summer and winter blends too. Sometimes I wonder if it's even worth it. It seems like the increased usage of the winter blend would offset the supposed pollution savings. Yeah maybe each gallon pollutes less, but when you are using all that extra fuel, it's probably a wash. So then we're just wasting gas to "not pollute". Stupid politicians.

[T-Mill]

Re: The Great Gasoline Tank Mystery!

Oh, there are many different mixtures. Summer blend, winter blend, E10, all kinds of stuff. Don't be so quick to discount that from happening.

But aren't the different blends designed to compensate for the "volume" change because of temperature differences? I'm not saying it is, I'm curious...

If anyone listens to Clark Howard, he was talking about this a while back and named a few stations, I think Cosco was one of them, that compensates their pumps for the discrepancy between hot gas and cold gas. He said that most of them didn't compensate, though...

[cam98aro]

Re: The Great Gasoline Tank Mystery!

But aren't the different blends designed to compensate for the "volume" change because of temperature differences? I'm not saying it is, I'm curious...

If anyone listens to Clark Howard, he was talking about this a while back and named a few stations, I think Cosco was one of them, that compensates their pumps for the discrepancy between hot gas and cold gas. He said that most of them didn't compensate, though...

no, they have different additives in them, since cars have a harder time starting in the winter, there are more evaporates in the fuel, while they arent there in the summer.

if you try to start a car with "summer fuel' on the coldest winter day it might have a hard time starting... but today with the fuel injection its not much of a problem.