2021 GMC Sierra Gas Tank Size

The typical 2021 GMC Sierra gas tank size is 24 or 28 gallons, depending on the model you drive.
Written by Kara Vanderbeek
Reviewed by Jessica Barrett
In the 2021 GMC Sierra 1500, the fuel tank capacity is either 24 or 28 gallons, depending on the trim level and model options of your truck
When it’s that time to refill your tank, it’s helpful to know how much gas you’ll need to put in. If you’re unsure how big your tank is, your owner’s manual should tell you your GMC’s exact fuel tank capacity. 
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How big is the gas tank on a 2021 GMC Sierra?

While the GMC Sierra’s large gas tank can save you trips to the gas station, the exact mileage of your GMC will depend on whether you’re highway or city driving, as well as which trim level and model options you’ve selected for your truck.
On a full tank of fuel, the 2021 GMC Sierra 1500’s maximum range for city driving is 336 to 528 miles, depending on the trim level. On the other hand, this GMC’s maximum range for highway driving is between 480 and 624 miles, depending on the trim level.
Listed below are some of the trims with a 24-gallon fuel tank
  • SLE 4dr Crew Cab 4WD 5.8 ft. SB
  • SLE 4dr Crew Cab4WD 6.6 ft. SB
  • 4dr Double Cab SB
  • Elevation 4dr Double Cab 4WD SB
  • Elevation 4dr Double Cab SB
For the following trims, the fuel tank size is 28 gallons:
  • 2dr Regular Cab 4WD LB
  • 2dr Regular Cab LB

How to check your 2021 GMC Sierra’s gas tank size

If you’re still not sure how many gallons you can fill your Sierra with, don’t worry: there are a few easy ways you can check your tank size so you can fuel your truck with confidence. 

Measure the gas tank

Want to measure the size of your gas tank yourself? Just grab a measuring tape and a calculator! Using your tape, measure the width, length, and height of the tank. Multiply each measurement together and divide the resulting number by 231 (that’s the number of cubic inches in a gallon). That’s your fuel tank capacity!

Check your owner’s manual

If math isn’t your thing, you can always look up the size of your gas tank in your owner’s manual. Typically, you can find the measurement under phrases like “fuel tank capacity”. 

Drive till empty, then fill it up

While this option is often an unintentional side effect of forgetting to fill up, you can find the gas tank size of your vehicle by driving until you hit “E”. Although this method of measurement isn’t quite as exact, you’ll get a good sense of the size of your tank—just don’t drive too long on empty! 
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How to save on fuel costs in a GMC Sierra

The 2021 GMC Sierra 1500 gets up to 22 mpg on the highway and 19 mpg in the city, depending on trim, which isn’t too shabby for a full-size pickup truck. Nevertheless, it doesn’t hurt to save at the pump when you can. Use the following tricks to keep your fuel costs to a minimum:
  • Keep up with regular maintenance to keep your truck performing at its best, and in turn, maintain your truck’s fuel economy.
  • Drive carefully. Avoid harsh accelerations, jerky braking, and stop-and-go traffic to keep your fuel consumption low. 
  • Avoid idling, especially in cold weather. Idling uses more fuel than restarting your car and gives off more pollution than when your truck’s in motion. Keep your engine off as much as possible to save fuel. 

How to optimize your GMC Sierra’s insurance coverage

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