How to Read a Gas Gauge

You can read a gas gauge by looking at how close the gauge needle is to the E marking—that will tell you how soon you’ll run out of gas.
Written by Patrick Price
Reviewed by Melanie Reiff
The gas gauge on your gauge cluster indicates the fuel level in your gas tank. It’s made up of nine lines that each represent one-eighth of a tank of gas. Keeping an eye on your fuel gauge is critical for keeping track of the amount of fuel you have remaining—so you don’t run out of gas! 
The car fuel gauge or “gas meter” in your vehicle is located in the instrument cluster—a collection of analog gauges positioned directly above the steering wheel. The gauge interprets information from the sensing system and shows you the amount of gas that you have remaining so you can refill once you reach low fuel levels
If you’ve never used a gas meter before, it can be a bit confusing to make sense of what all the tick marks, fractions, and letters represent. Not to worry—
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Where is my gas gauge?

The gas gauge is located in the instrument cluster or “gauge cluster,” as it’s sometimes called. The cluster is located on the driver's side of the dashboard and has several gauges including the speedometer, the odometer, and of course the fuel gauge. 

How does a fuel gauge work?

The fuel gauge, also known as the fuel level sensor, alerts the driver to the current level of gasoline in their gas tank—which lets them know when it’s time to fill up at a gas station. It works by constantly reading the level of reserve fuel remaining in the gas tank and sending that information to a readable gauge on the dashboard. 
The fuel gauge is made up of two components: the sensor system (or “sender”) and the indicator (or “gauge”). 
The sender reads the gallons of gas present in the fuel tank using the variable resistor, float switch, and wiper. Based on the total capacity of the tank, that reading is converted into a fraction—which indicates what percentage of the tank is full. That fraction is then conveyed to the indicator. 
The indicator raises or lowers the needle to the appropriate position between the E marker (representing an empty tank) and the F marker (indicating the top of the tank). 

How to read your gas gauge

The gas gauge is very easy to read. All you need to do is look at the needle’s position on the gauge. The closer it is to F, the fuller your gas tank is. On the other hand, the closer the needle gets to E, the more empty your tank is.  
The gauge is marked by nine lines or “tick marks,” each of which represents an increment of one-eighth of a tank. The larger lines indicate an empty tank and a full tank—as well as the one, two, and three-quarters full levels. 

What does my gauge reading mean?

Each of the lines on your fuel gauge represents a specific fraction relative to the current amount of gas you have remaining. From bottom to top, these marks indicate an empty tank, ⅛ of a tank, ¼ of a tank, ⅜ of a tank, ½ tank, ⅝ of a tank, ¾ of a tank, ⅞ of a tank, and a full tank of gas. 
For instance, if your car has a 20-gallon tank and it currently has five gallons of gas, you will see the needle at the third tick mark up from empty—indicating that you have ¼ of a tank of gas remaining. 
In general, you should fill up at a gas station as soon as possible whenever your tank drops below ¼ tank.

Troubleshooting a faulty gas gauge

A gas gauge is a crucial tool for proper vehicle operation. Without it, you’ll be left in the dark as to how much fuel you have remaining. If your gas gauge is malfunctioning, try to figure out and resolve the issue as soon as possible. 

Knowing when your gas gauge is malfunctioning 

It’s fairly easy to notice when there’s something off with your fuel gauge. Any time you have a fairly accurate idea of your fuel level and the gauge isn’t giving the reading you’d expect, there’s probably some sort of malfunction. 
Here are some of the most common warning signs of a faulty gas gauge:
  • The fuel gauge is reading empty when you’ve recently filled up at a gas station 
  • The fuel gauge is stuck at the full marker and stays there regardless of how much you drive
  • The fuel gauge constantly shifts between the F and the E marker 
  • The fuel gauge consistently gives readings that are obviously inaccurate 

Resolving fuel gauge errors

Unfortunately, noticing that your gas gauge is malfunctioning is much easier than diagnosing the exact cause of the error. If you’re lucky, resetting the gauge will fix the problem—but often, it will not. In this case, you can do a bit of DIY troubleshooting if you have a multimeter.
The gas gauge system is based on electrical components, and errors usually have something to do with faulty wiring or fried circuits. The majority of gas gauge malfunctions can be linked to a faulty instrument cluster, a failing gas gauge circuit, a bad/blow fuse, disconnected wires, frayed or faulty wiring between the sender and the indicator, or a defective sending unit
If you have some experience with automotive electronics, you can test each of these components with a multimeter to determine where the issue lies. Some modern cars even have a self-diagnosis switch for determining the root of gauge failures. But before using that, it's a good idea to reset your fuel gauge and see if that resolves the issue. 
Here’s how to reset your gas gauge:
  • Turn the ignition to the ON position, but do not start the engine
  • Press the Trip/ODO button. This will put the odometer into ODO mode
  • Turn the ignition back to the OFF position
  • Press and hold the Trip/ODO button. While holding the button down, turn the ignition back to the ON position
  • Press and release the Trip/ODO button three times. On the third time, hold it down. Keep holding down the button for about five seconds, until the odometer shows your car’s leveling information. Once the leveling information pops up, release the button
  • Press and hold the Trip/ODO button again. After a few seconds, the odometer should display the number 1—this means the reset process has started. Continue holding down the Trip/ODO button 
  • When the odometer returns to its normal display, the reset is complete—at this point, you can release the Trip/ODO button 
Sometimes, resetting the gauge will sort out your issue. If not, it might be time to have an automotive electrician look at your gas gauge. 

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The current fuel level in your gas tank is measured by the fuel-sending unit—which then conveys the information to the indicator gauge on your dashboard.
A quarter tank is a term that describes a gas tank that is one-quarter of the way full, meaning it only has 25% of its total fuel capacity remaining. A three-quarter tank refers to a tank that is three-quarters of the way full, meaning 75% of its gas tank is full.
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