Definitive Gas Tank Capacity

Joined
11 February 2003
Messages
490
Location
Denver, Colorado, USA
There must be several dozen threads on "Gas Tank Capacity," "How Much Gas is in the Tank When the Warning Light Comes" on, and so on. Here is the definitive answer – but first a short explanation.

On my 25 state, 33 day, 7700 mile road trip I recently completed, I was in Medora, ND, “Gateway to Roosevelt National Park,” population 100 – except in summer when it can grow to several thousand. Medora is a great place, and I’ll post more information about when I finally finish documenting this trip.

The fuel light had been on about 35 miles or so, however there was no 91+ octane in this northern metropolis. I was told 15 miles up I-94 I in Belfield, ND could get whatever gas I wanted. I departed without a second thought.

About half way there the engine momentarily lost power, and I thought, “Oh ---,” well you know what I thought.

I never stopped the car. I put it in neutral and shut off the engine – dead stick coasting --down to about 30 mph. For the rest of the trip I just jump started the engine and accelerated very very slowly to about 50 (or whatever speed the engine started sputtering again.) I repeated this about 10 times and made it to a gas station, coasting up to the gas pump. This was a technique used in the Mobil Gas Economy Runs back in the 1950s; mega-hypermiling. It makes no sense for normal traveling, but got me out of this jam.

The results: 17.89 gallons is the official tank capacity. (Factory says 18.1 and I’ll bet that is spot on. You can never totally empty the gas tank without opening the drain plug.) For how many miles can you go after the fuel light comes on, it depends upon what you call "fuel light comes on." From when you first see it glow, I guess it is about 55 - 60 miles. From it coming on steadly -- and staying on, it is about half that.
I also noticed that the fuel type drastically affected the mileage I got, varying from about 24 to 32 mpg. Different states have different pollution requirements, and use different percentages of ethanol in their gasoline. In ND, MN and WI, premium was actually less expensive than regular, I’m sure because of the ethanol content.

So there you go: Distance left at fuel light first lighting (dimly) is about 55 miles, at about 28 mpg average. Use this information as you will, and don’t blame me if “your mileage may differ.”

Here is the "proof."

showphoto.php
 
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Here is a trick I learned when I was a service tech.

Some people are afraid the garage will go joyriding with your car when you drop it off for service and leave their car with so very little fuel so you can't go far with their car. Well , some people take that to the extreme. I have been in customer's cars with so little fuel it would run out with just a simple around the block road test under 1 mile.

With modern fuel injected cars the electric fuel pump will deliver the fuel down to the last drop unlike a mechanical fuel pump. As the car sputters as it is runs out of fuel if you quickly jerk the steering wheel back and forth to make the car ' wiggle ' it will allow the fuel pump to get that last bit of fuel it normally would not be able to get on flat normal driving. Basically you are sloshing that last bit of fuel over to the pickup and the fuel pump sucks air then fuel then air then fuel just enough to keep the engine running. It can keep you from walking if you are fairly close to a gas station.

This happened several times to me with customer's cars. I would get it to a gas station and put 1/10 of a gallon of fuel in it to get back to the dealership. Yep , you read that right 1/10 of a gallon of fuel - no more. The gas station hated you when you bought 1/10 of a gallon ... lol .

When the customer picked up the car , we would not tell them it ran out of gas. Most of them would pull out of the dealership and get less than a mile down the road and run out of gas. Some of them would walk back or get towed. They would be pissed. Only then would we tell them that they left us with a car that was on fumes and it was their fault and we could prove it because we had the mileage when they dropped their car off and the mileage when we were done working on the car. The red flag came up when you went out to pull the car into the bay to work on it and the fuel light was already on before you preformed service. We would have the service manager double check and verify the mileage while the car was in the service bay before the road test.

We would also tell them that they should have left the car with enough fuel for a short 1 mile road test and how bad this was for the injectors and fuel pump.

If you are afraid the garage was going to go joyriding with your car , just write down the mileage. Don't leave it with no fuel in the tank. Some car owners are idiots !!!
 
I guess that in tank fuel pumps don't like sipping the last amount of fuel. Another thing is that the fuel pump is being cooled by the surrounding gas. It doesn't get 'hot' but it works at higher temperature are therefore with more wear. Just a thought.
 
There must be several dozen threads on "Gas Tank Capacity," "How Much Gas is in the Tank When the Warning Light Comes" on, and so on. Here is the definitive answer – but first a short explanation.

On my 25 state, 33 day, 7700 mile road trip I recently completed, I was in Medora, ND, “Gateway to Roosevelt National Park,” population 100 – except in summer when it can grow to several thousand. Medora is a great place, and I’ll post more information about when I finally finish documenting this trip.

The fuel light had been on about 35 miles or so, however there was no 91+ octane in this northern metropolis. I was told 15 miles up I-94 I in Belfield, ND could get whatever gas I wanted. I departed without a second thought.

About half way there the engine momentarily lost power, and I thought, “Oh ---,” well you know what I thought.

I never stopped the car. I put it in neutral and shut off the engine – dead stick coasting --down to about 30 mph. For the rest of the trip I just jump started the engine and accelerated very very slowly to about 50 (or whatever speed the engine started sputtering again.) I repeated this about 10 times and made it to a gas station, coasting up to the gas pump. This was a technique used in the Mobil Gas Economy Runs back in the 1950s; mega-hypermiling. It makes no sense for normal traveling, but got me out of this jam.

The results: 17.89 gallons is the official tank capacity. (Factory says 18.1 and I’ll bet that is spot on. You can never totally empty the gas tank without opening the drain plug.) For how many miles can you go after the fuel light comes on, it depends upon what you call "fuel light comes on." From when you first see it glow, I guess it is about 55 - 60 miles. From it coming on steadly -- and staying on, it is about half that.
I also noticed that the fuel type drastically affected the mileage I got, varying from about 24 to 32 mpg. Different states have different pollution requirements, and use different percentages of ethanol in their gasoline. In ND, MN and WI, premium was actually less expensive than regular, I’m sure because of the ethanol content.

So there you go: Distance left at fuel light first lighting (dimly) is about 55 miles, at about 28 mpg average. Use this information as you will, and don’t blame me if “your mileage may differ.”

Here is the "proof."

showphoto.php

Great story Mark, can't wait to hear more from your trip. You've got to be closing in on 200k by now right?
 
Never knew trying to run out of gas could be so much fun.

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Running on a empty tank and running out of gas is not good for your fuel pump and injectors.

People say this like it's gospel and never back it up with any evidence or facts. I'm not saying it's not true, but I'm a natural skeptic whenever I see something like this repeated over and over.
 
Depends on the car I think. I know on LT1/LS1 Camaros the fuel acts as a lubricant for the fuel pump. If you run the car empty the fuel pump will seize. Lots of stories about that in the f-body forum. Haven't heard about it being bad for injectors.
 
Craig

433 miles. It was pretty lousy gas mileage, but there was a strong EAST wind that day.

The Trip Diary is progressing. I had camera problems (operator error), so I'm doing a fair bit of photo manipulating, as well as adding pictures from all over the web of things I didn't photograph during the trip.

Being gone 33 days does some good things to your head, and writing about it is even better.

Hope all is well with you and yours.

Mark
 
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