- Newest year: 2009
- Gas
- Midsize cars
2008-2009 Cadillac STS MPG & Fuel Cost
2 model years · 16–20 MPG combined
15,000 mi/yr · regular gasoline $4.36/gal (U.S. average, Sep 2026)
Cheaper to fuel than 5 of 10 midsize car configurations, MY2009. Ranked against all rated configurations, not sales-weighted.
2008-2009 Cadillac STS at a glance
The 2008-2009 Cadillac STS covers 2 model years in the EPA database (8 configurations in all), rated 16–20 MPG combined. The newest model year, 2009, costs about $3,270 a year to fuel for its most efficient version, the STS 3.6L 6-cyl RWD (20 MPG), at regular gasoline $4.36/gal (U.S. average, Sep 2026). EPA changed the ratings in 2009.
2008-2009 Cadillac STS by model year
What the 2009 STS 3.6L 6-cyl RWD costs to drive
Per month
$273
$3,270 a year ÷ 12
Per 25 miles
$5.45
Per 100 miles
$21.80
Five years
$16,350
5 × the yearly cost, prices held at today's level
vs the midsize car median
Same
Class median $3,270 a year, MY2009
Based on 15,000 miles a year and regular gasoline $4.36/gal (U.S. average, Sep 2026).
2009 Cadillac STS MPG
Versus 2008: The most efficient configuration stays at 20 MPG. Its annual cost stays at $3,270.
Gas configurations (4)
| Trim | Engine | Drive | City | Hwy | Comb. | $/yr |
|---|---|---|---|---|---|---|
| STS 3.6L 6-cyl RWD (Most efficient) | 3.6L 6-cyl | RWD | 17 | 26 | 20 | $3,270 |
| STS 3.6L 6-cyl 4WD | 3.6L 6-cyl | 4WD | 17 | 26 | 20 | $3,270 |
| STS 4.6L 8-cyl RWD | 4.6L 8-cyl | RWD | 15 | 24 | 18 | $4,460 |
| STS 4.6L 8-cyl 4WD | 4.6L 8-cyl | 4WD | 15 | 22 | 17 | $4,730 |
2 configurations require or recommend higher-octane gasoline and are costed at premium gasoline $5.36/gal (U.S. average, Sep 2026).
2008 Cadillac STS MPG
16–20 MPG · $3,270–$5,020/yr
Gas configurations (4)
| Trim | Engine | Drive | City | Hwy | Comb. | $/yr |
|---|---|---|---|---|---|---|
| STS 3.6L 6-cyl RWD (Most efficient) | 3.6L 6-cyl | RWD | 17 | 26 | 20 | $3,270 |
| STS 3.6L 6-cyl 4WD | 3.6L 6-cyl | 4WD | 17 | 26 | 20 | $3,270 |
| STS 4.6L 8-cyl RWD | 4.6L 8-cyl | RWD | 15 | 24 | 18 | $4,460 |
| STS 4.6L 8-cyl 4WD | 4.6L 8-cyl | 4WD | 14 | 21 | 16 | $5,020 |
2 configurations require or recommend higher-octane gasoline and are costed at premium gasoline $5.36/gal (U.S. average, Sep 2026).
Fuel cost by state
Yearly cost of the STS 3.6L 6-cyl RWD: $4,440 in California and $2,850 in Texas, a $1,590 difference.
- California $4,440
- Washington $4,120
- New York $3,270
- Florida $3,090
- Texas $2,850
Similar cars
Closest combined MPG among MY2009 midsize car models.
Generations
Frequently asked questions
What gas mileage does the 2008-2009 Cadillac STS get?
EPA rates the 2008-2009 Cadillac STS at 16–20 MPG combined across 8 configurations and 2 model years. The most efficient version, the 2009 STS 3.6L 6-cyl RWD, is rated 20 MPG (17 city, 26 highway).
Which years had the best MPG in the 2008-2009 Cadillac STS?
Every model year of the 2008-2009 Cadillac STS tops out at 20 MPG combined, so no year is better than another.
Did EPA ratings change during the 2008-2009 Cadillac STS?
Yes. Ratings changed in 2009.
How does the 2008-2009 Cadillac STS compare with the previous generation?
The previous generation (2007 Cadillac STS) is rated 16–19 MPG combined and costs $3,440–$5,020 a year to fuel; the 2008-2009 model is rated 16–20 MPG and costs $3,270–$5,020 a year.
How much does it cost to fuel a 2009 Cadillac STS per year?
Driving 15,000 miles a year at regular gasoline $4.36/gal (U.S. average, Sep 2026), the STS 3.6L 6-cyl RWD costs about $3,270 a year. Across all 4 configurations the cost runs $3,270–$4,730 a year. That is a $1,460 difference between the cheapest and the costliest configuration.
How much does it cost to drive a 2009 Cadillac STS 100 miles?
About $21.80 per 100 miles for the STS 3.6L 6-cyl RWD at regular gasoline $4.36/gal (U.S. average, Sep 2026), and between $21.80 and $31.53 across all configurations. That is the annual cost over 15,000 miles divided by 150.
Is the 2009 Cadillac STS more efficient in the city or on the highway?
The STS 3.6L 6-cyl RWD is rated 17 city and 26 highway MPG, so it is more efficient on the highway, by 9 MPG.
How does the 2009 Cadillac STS compare with other midsize car configurations?
The STS 3.6L 6-cyl RWD costs about $3,270 a year to fuel, the same as the class median of $3,270, and less than 5 of 10 midsize car configurations. The comparison covers all 130 rated midsize car configurations for MY2009, not weighted by sales.
Is the 2009 Cadillac STS different from the 2008 model?
The most efficient configuration stays at 20 MPG. Its annual cost stays at $3,270. EPA lists 4 configurations for 2009 against 4 configurations for 2008. See the 2008 Cadillac STS for that year.