2020 GMC Sierra Cab Chassis 2WD MPG & Specs — Real-World vs EPA, All Trims
Every trim takes regular — no premium needed.
Is the 2020 GMC Sierra Cab Chassis 2WD good on gas?
At up to 17 MPG combined, the 2020 GMC Sierra Cab Chassis 2WD is worse than average for a Special Purpose Vehicle 2WD — that class averages about 18.4 MPG across 746 EPA-tested versions, so it's on the thirsty side for its size.
Real-world MPG vs the EPA number
The EPA figures above come from a standardized dynamometer test, not the open road — real-world MPG typically runs a bit lower depending on your driving, climate and terrain. That's true of every car on this site, old or new.
At today's AAA national average price — $3.80/gal for regular gas as of 2026-07-05 — the most efficient trim runs about $3,353/year (roughly $279/month, about $22.35 per 100 miles) at the EPA's assumed 15,000 miles/year, using an estimated 882 gallons a year. We don't estimate a cost-per-fill since exact tank size isn't in the public EPA dataset, but the per-100-mile figure scales to any tank. Current national average gas prices →
2020 GMC Sierra Cab Chassis 2WD trims & fuel economy
| Trim (engine / transmission) | Fuel | MPG | Fuel/yr (today's price) |
|---|---|---|---|
| 4.3L 6-cyl, Automatic 6-spd, RWD | REGULAR | 17 | $3,353 |
| 5.3L 8-cyl, Automatic 6-spd, RWD | REGULAR | 15 | $3,800 |
2020 GMC Sierra Cab Chassis 2WD specs
What the EPA test-car listings record for this model year — every combination sold is a row in the trims table above.
| Engine options | 4.3L 6-cyl · 5.3L 8-cyl |
| Transmission | Automatic 6-spd |
| Drive type | RWD |
| EPA body class | Special Purpose Vehicle 2WD |
| Fuel | Regular |
| Tailpipe CO₂ | 523–582 g/mi |
Other years of the GMC Sierra Cab Chassis 2WD
Similar cars (Special Purpose Vehicle 2WD)
Cars that take premium · Cheapest cars to fuel · Where fuel grade depends on the trim · Fuel guides
2 trim(s) · EPA FuelEconomy.gov data retrieved 2026-07-24 · fuel prices AAA national average as of 2026-07-05.