The GMC Sierra does 18.7 mpg combined (16.7 city, 21.7 highway), which works out to about $2,053 a year in fuel at $3.20 a gallon and 12,000 miles. Engine choice matters more than you'd think: 3L 6-cyl does 25.7 mpg while 5L 8-cyl does 15.5 — a difference of $983 a year. Against other V6 cars it sits below the average of 19.9 mpg.
Every GMC Sierra engine, compared
Gas mileage on the GMC Sierra ranges from 25.7 down to 15.5 depending on which engine sits under the bonnet — a spread of $983 a year across 10 versions of the same car. Picking the right one often saves more fuel than picking a different car altogether. Yearly cost assumes 12,000 miles at $3.20 a gallon.
| Engine | Combined | City / Highway | Years | Fuel per year |
|---|---|---|---|---|
| 3L 6-cyl | 23.1 / 29.3 | 2020–2026 | $1,494 | |
| 6L 8-cyl Hybrid | 20.4 / 22.6 | 2009–2013 | $1,811 | |
| 2.7L 4-cyl | 19 / 22.1 | 2019–2026 | $1,892 | |
| 6.2L 8-cyl | 16.8 / 22.4 | 1989–1993 | $2,021 | |
| 5.3L 8-cyl Hybrid | 16.9 / 21.1 | 2004–2018 | $2,098 | |
| 5.3L 8-cyl | 15.8 / 21.9 | 2007–2026 | $2,098 | |
| 6.5L 8-cyl | 16.3 / 21 | 1994–1996 | $2,133 | |
| 4.3L 6-cyl | 15.5 / 20.7 | 1989–2019 | $2,182 | |
| 4.8L 8-cyl | 14.4 / 19 | 1999–2006 | $2,356 | |
| 5L 8-cyl | 14 / 18.5 | 1997–1998 | $2,477 |
What that actually costs
The GMC Sierra burns a gallon every 18.7 miles, so 12,000 miles takes about 642 gallons a year. At $3.20 that is what the table below adds up to.
| Measure | Value |
|---|---|
| Cost per mile | $0.171 |
| Fuel per year | $2,053 |
| Fuel over five years | $10,265 |
| Against other V6 cars | +$123 a year |
| EPA's own estimate | $3,488 a year |
City or highway — who is this car for
The GMC Sierra gives up 5 mpg the moment you leave the motorway — 21.7 out there against 16.7 in town, a 30% drop worth $529 a year. A wide gap punishes stop-and-start traffic; a narrow one means the car doesn't care where you drive it.
| Measure | Value | Reading |
|---|---|---|
| City | 16.7 mpg | $2,299 a year if you only drive in town |
| Highway | 21.7 mpg | $1,770 a year if you mostly commute |
| Gap | +5 mpg (30%) | Wide — this car dislikes traffic |
How the Sierra changed over the years
The Sierra peaked in 2020 at 22.3 mpg (20 city, 25.7 highway) and was at its thirstiest in 2003 at 16 — 6.3 mpg apart, or $678 a year in fuel between buying one year and the other. The 2026 car does 21. Jumps usually mark a new generation or a new engine; dips often mean a heavier body or added all-wheel drive.
| Model year | Combined | City / Highway | Engines offered | Fuel per year |
|---|---|---|---|---|
| 2026 | 19 / 23.3 | 3 | $1,829 | |
| 2025 | 19 / 23.7 | 3 | $1,829 | |
| 2024 | 19 / 23.7 | 3 | $1,829 | |
| 2023 | 19.7 / 23.7 | 3 | $1,803 | |
| 2022 | 19.3 / 24.3 | 3 | $1,803 | |
| 2021 | 20 / 25.3 | 3 | $1,745 | |
| 2020 | 20 / 25.7 | 3 | $1,722 | |
| 2019 | 17.7 / 22.3 | 3 | $2,021 | |
| 2018 | 17.3 / 23.7 | 3 | $1,949 | |
| 2017 | 17.3 / 23.7 | 3 | $1,949 | |
| 2016 | 17.3 / 23.3 | 3 | $1,949 | |
| 2015 | 17 / 23.5 | 2 | $1,969 | |
| 2014 | 17 / 23 | 2 | $1,969 | |
| 2013 | 16.7 / 21.7 | 3 | $2,053 | |
| 2012 | 16.7 / 21.7 | 3 | $2,053 | |
| 2011 | 16.7 / 21.7 | 3 | $2,053 | |
| 2010 | 17 / 21.3 | 3 | $2,021 | |
| 2009 | 17 / 21 | 3 | $2,098 | |
| 2008 | 15 / 20 | 2 | $2,259 | |
| 2007 | 15.3 / 19.3 | 3 | $2,259 | |
| 2006 | 15.3 / 19.3 | 3 | $2,259 | |
| 2005 | 15 / 19.3 | 3 | $2,299 | |
| 2004 | 15 / 19 | 3 | $2,356 | |
| 2003 | 14 / 19 | 2 | $2,400 | |
| 2002 | 14 / 18.5 | 2 | $2,400 | |
| 2001 | 14.5 / 19.5 | 2 | $2,327 | |
| 2000 | 14.5 / 20 | 2 | $2,259 | |
| 1999 | 14.5 / 20 | 2 | $2,327 | |
| 1998 | 15 / 19.5 | 2 | $2,327 | |
| 1997 | 14.5 / 20 | 2 | $2,259 |
MPG is a number. Dollars per year is the answer.
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How we count
This page rests on 96 EPA ratings of the GMC Sierra — 10 engines across 1989–2026. The mileage is EPA's laboratory figure, unchanged; the yearly bill is ours, at 12,000 miles and $3.20 a gallon, against EPA's own estimate of $3,488. Full method.
Frequently asked questions
What mpg does the GMC Sierra get?
18.7 mpg combined on average — 16.7 in the city and 21.7 on the highway, per EPA ratings across 1989–2026.
How much does a GMC Sierra cost in fuel per year?
About $2,053 at 12,000 miles and $3.20 a gallon — roughly $10,265 over five years, or 0.171 dollars a mile.
Which Sierra engine is the most economical?
The 3L 6-cyl at 25.7 mpg, against 15.5 for the 5L 8-cyl — a difference of about $983 a year.
Is the Sierra good on fuel compared with similar cars?
Against other V6 cars it sits below the average of 19.9 mpg, computed across 4940 ratings.
Are these real-world Sierra figures?
No — they are EPA laboratory ratings, the same ones printed on the window sticker, and EPA's own annual fuel estimate for the GMC Sierra is $3,488 against the $2,053 we compute at 12,000 miles. Expect a little worse in practice: the spread between the 26 and 15 mpg versions of this car is smaller than the spread between two drivers of the same one.
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