2008 GMC Sierra K15 4WD MPG & Specs — Real-World vs EPA, All Trims
Fuel grade varies by trim — see the breakdown below.
Is the 2008 GMC Sierra K15 4WD good on gas?
At up to 16 MPG combined, the 2008 GMC Sierra K15 4WD is about average for a Standard Pickup Trucks 4WD — that class averages about 16.5 MPG across 1,581 EPA-tested versions, so it's middle-of-the-road 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 $3,562/year (roughly $297/month, about $23.75 per 100 miles) at the EPA's assumed 15,000 miles/year, using an estimated 938 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 →
2008 GMC Sierra K15 4WD trims & fuel economy
| Trim (engine / transmission) | Fuel | MPG | Fuel/yr (today's price) |
|---|---|---|---|
| 4.8L 8-cyl, Automatic 4-spd, AWD | REGULAR | 16 | $3,562 |
| 5.3L 8-cyl, Automatic 4-spd, AWD | REGULAR | 16 | $3,562 |
| 4.3L 6-cyl, Automatic 4-spd, AWD | REGULAR | 15 | $3,800 |
| 6.0L 8-cyl, Automatic 4-spd, AWD | REGULAR | 14 | $4,071 |
| 5.3L 8-cyl, Automatic 4-spd, AWD | FLEX-FUEL | 16 | $3,900 |
2008 GMC Sierra K15 4WD 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 | 4.8L 8-cyl · 5.3L 8-cyl · 4.3L 6-cyl · 6.0L 8-cyl |
| Transmission | Automatic 4-spd |
| Drive type | AWD |
| EPA body class | Standard Pickup Trucks 4WD |
| Fuel | Varies by trim |
Other years of the GMC Sierra K15 4WD
Similar cars (Standard Pickup Trucks 4WD)
Cars that take premium · Cheapest cars to fuel · Where fuel grade depends on the trim · Fuel guides
5 trim(s) · EPA FuelEconomy.gov data retrieved 2026-07-24 · fuel prices AAA national average as of 2026-07-05.