GMC T15 (S15) Pickup 4WD
18.5 MPG The 1988 GMC T15 (S15) Pickup 4WD is EPA-rated at 18.5 MPG combined (16.3 city / 22.3 highway). Over 15,000 miles a year that is about 811 gallons, $2595 a year in fuel, or $0.173 per mile at $3.20/gal.
Across its full 1984–1988 run it averages 18.5 MPG, essentially flat across 5 model years.
Running cost at different fuel prices and mileages
The figure everyone actually wants, and the one the EPA does not publish — because it depends on a fuel price no agency will commit to.
| Fuel price | Per mile | 10,000 mi/yr | 15,000 mi/yr | 20,000 mi/yr |
|---|---|---|---|---|
| $2.50/gal | $0.135 | $1351 | $2027 | $2703 |
| $3.00/gal | $0.162 | $1622 | $2432 | $3243 |
| $3.20/gal | $0.173 | $1730 | $2595 | $3459 |
| $3.50/gal | $0.189 | $1892 | $2838 | $3784 |
| $4.00/gal | $0.216 | $2162 | $3243 | $4324 |
| $4.50/gal | $0.243 | $2432 | $3649 | $4865 |
| $5.00/gal | $0.270 | $2703 | $4054 | $5405 |
Every model year
| Year | Combined | City | Highway | EPA fuel cost/yr | CO₂ g/mi | Trims |
|---|---|---|---|---|---|---|
| 1988 | 18.5 MPG | 16.3 | 22.3 | $3367 | 482 | 6 |
| 1987 | 18.2 MPG | 16.3 | 21.5 | $3450 | 494 | 6 |
| 1986 | 18.8 MPG | 16.5 | 22 | $3333 | 477 | 6 |
| 1985 | 18.2 MPG | 16.1 | 21.9 | $3428 | 490 | 9 |
| 1984 | 18.6 MPG | 16.4 | 22.3 | $3350 | 480 | 10 |
Where a model year offered several engines or drivetrains, the figure is the average across all EPA-tested trims that year — the trim count is shown so you can see how much averaging is involved.
How it compares in its class
Among the 29 standard pickup trucks models tracked here, the GMC T15 (S15) Pickup 4WD ranks 1 on current figures, against a class average of 15.4 MPG.
Nothing in its class is rated higher — it leads the group.
Tailpipe CO₂ is rated at 482 grams per mile, which works out to roughly 7.2 tonnes a year at 15,000 miles.
Questions
What MPG does the GMC T15 (S15) Pickup 4WD get?
The 1988 GMC T15 (S15) Pickup 4WD is rated at 18.5 MPG combined by the EPA — 16.3 city and 22.3 highway. Across all 5 model years in the database it averages 18.5 MPG, ranging from 16 to 21 depending on year and trim.
How much does a GMC T15 (S15) Pickup 4WD cost in fuel per year?
At 18.5 MPG and 15,000 miles a year, it burns about 811 gallons — roughly $2595 a year with fuel at $3.20 a gallon, or $0.173 per mile. The EPA's own published annual figure for the 1988 model is $3367.
Has the GMC T15 (S15) Pickup 4WD become more efficient over time?
Barely. It sits at 18.5 MPG today against 18.6 in 1984 — essentially flat across 5 model years, with efficiency gains offset by weight and power creep.
Is the GMC T15 (S15) Pickup 4WD efficient for its class?
It ranks 1 of 29 in the Standard Pickup Trucks class on current figures, against a class average of 15.4 MPG. That is 3.1 better than typical for the class.
EPA test figures from fueleconomy.gov. Cost per mile and annual fuel spend are computed at a reference price of $3.20 per gallon — use your own price. Estimates based on official test figures and average fuel prices. Real-world consumption varies with driving style, load, terrain and maintenance.