How Big Is My Fuel Tank? [3 Ways To Determine Its Size]

When attempting to calculate your vehicle's fuel economy on your own, you'll need to know the size of your fuel tank. Doing the math to determine how many miles per gallon you are burning should always start with a full tank. If you are wondering how large your fuel tank is, we can help you make that determination. We researched vehicles from numerous professional sources so that you can have a definitive answer.

The size of your vehicle's fuel tank can be determined in one of three ways:

• Checking inside your owner's manual
• Filling up after being empty
• Measuring the tank itself

Now that we know the three methods in determining how much fuel your vehicle's fuel tank will hold, we'll take a closer look at each one. You might be wondering if you should always keep your fuel tank full or if your vehicle will run better with a full tank of gasoline. How does the gas pump know when the gas tank is full? Which SUV has the largest fuel tank? For the answers to these questions and more, read ahead in this post to see what our answers have uncovered. 

Things You Might Not Know About Your Vehicle's Fuel Tank

Earlier in this post, we listed the three ways you can determine how big your vehicle's fuel tank is. Let's take a closer look at each method.

Checking inside your owner's manual

This is by far the easiest method in determining your vehicle's fuel capacity. If you have your owner's manual handy, it will have this number listed. Check in the table of contents, and look for "fuel tank" or "fuel economy." After some page-turning, you'll be able to have the answer directly from the manufacturer.

But perhaps you've misplaced the owner's manual. Or maybe you have an older model car that you purchased used and never had one to begin with. No worries. There are still two other methods in finding out how much gas your vehicle will hold. 

Filling up after being empty

While a bit risky, this method will get you pretty close to determining the amount of fuel your vehicle can hold. Run your car below E, then fill it up. However many gallons it takes to get your tank back to Full is how many gallons your tank holds. 

Remember that the only sure-fire way to get the precise answer is to have your tank run TOTALLY empty. This means accepting certain risks that you probably shouldn't take. It would mean having a full gas can on hand to put enough fuel in your vehicle to get it back to a service station. Then adding that amount of fuel to the total amount that you pump into your vehicle once you are there.

Running your vehicle totally out of fuel can damage the fuel pump, so we don't recommend it.

Measuring the tank itself

This method of finding out your vehicle's fuel capacity will take a bit of time. You can measure the height, width, and depth of your fuel tank. These measurements can be used to figure out the liquid volume that the tank will hold. 

As you can see, getting the information from your owner's manual is the simplest and safest method.

Should you Keep your Gas Tank Full?

We recommend that you always keep your fuel tank as close to full as possible. There are several reasons for this, ranging from convenience to safety. Let's take a look at why we make this suggestion.

It could save you money

Running a vehicle on a tank of fuel that is close to empty can lead to some damage. Driving around habitually with an empty tank will definitely cost you some dollars. Fuel pump replacements, fuel injector cleanings, and more will make you pay plenty out of pocket for something you can easily avoid if you would just keep fuel in your tank.

It will save you time

Keeping your tank full makes it quick and convenient to get to where you are going. Filling a low tank takes a lot longer, and getting fuel to a tank that has been run totally dry will take even longer. 

Safety reasons

Who wants to run out of gas? Being stranded somewhere isn't safe, and neither is walking on the shoulder of a busy highway to get fuel from the nearest service station. Keeping that tank full will keep this from happening.

While technology makes those handy gas gauges more efficient, they can still malfunction from time to time. This means that even though it says your needle is on E, that it might actually be a bit lower. Don't run the risks. When your tank hits a quarter full, go ahead and start looking for a place to fill it up.

Fuel Economy 

Studies show that, even though a full tank of fuel is heavier, a full tank of gas will get better fuel economy than a nearly empty one. 

Mechanical issues

Your vehicle's fuel pump relies on the fuel to keep it lubricated and cooled. If the tank is nearly empty, it can begin to suck some air through this pump. This can damage it, making for a really inconvenient replacement. 

Whenever you run a car close to empty, you also allow any gunk or settled debris in the fuel tank to get sucked through the fuel pump. This can damage your fuel injectors, making them in need of a thorough cleaning or a replacement.

In colder weather, more damage can be done by running on a low tank of gas. The colder it is, the greater the chance for condensation to be sucked through the fuel pump. This will make it difficult for your vehicle to start and may cause it to stall.

Cars for Sale has a more in-depth explanation of each of the above reasons why you should keep your fuel tank full. 

Does your Car Run Better with a Full Tank of Gas?

Cars will definitely run better on a full tank of gas than an empty one. When your fuel tank is really low, the sludge and sediment that has accumulated at the bottom of the tank will be sucked into the fuel line and end up damaging your fuel injectors. While this can be taken care of with fuel injector cleaners in most cases, it can cause some long-term damage to this component.

A nearly dry tank will also suck air into the fuel pump. As the fuel pump needs lubrication and the cooling of the fuel, the pump will run too hot. This can create a situation in which the fuel pump locks up and seizes. When this happens, you'll need to replace the fuel pump.

How Does the Gas Pump Know When the Tank is Full?

Have you noticed how modern gas pumps will automatically shut off when the tank is full? This isn't done by magic. The gas pump will detect when the fuel in the tank has risen close to the top of the pump's tip.

This works by way of a secondary line inside the pump itself, called a venturi. How Stuff Works explains that...

...when the end of the venturi pipe becomes submerged in the rising gas, it chokes off the air pressure that holds the nozzle handle open and shuts down the flow of gas.

Which SUV has the largest fuel tank?

SUVs have fuel tanks that vary in size. Currently, the Chevy Suburban has the largest fuel tank for this class of vehicles. The Suburban's fuel tank will hold up to 31 gallons of gasoline.

As with SUVs, passenger trucks will have their fuel tanks vary from model to model. The Ford Super Duty class is the champion here, with a fuel tank that will hold up to 48 gallons.

In Closing

Checking the owner's manual is the fastest and easiest way to determine how big your fuel tank is. Be sure to keep your fuel tank more than a quarter full at all times, as letting it fall too low can lead to damaging your fuel pump, as well as dirtying up your fuel injectors. Vehicles will always function better on full tanks of gas, and keeping it reasonably full will save you from getting stranded on empty. Drive safe!

If you found this automotive post to be helpful, we believe you'll find these posts on vehicles to be informative:

How Hot Does A Combustion Chamber Get In A Vehicle? [The Answer Might Surprise You!]

What SUVs Have V6 Engines In 2021? [A Look At Midsize And Full-Size SUVs]

How Do I Keep My Car Smelling Good All The Time? (Inc. Best Car Air Fresheners!)