Against 456 other V6 cars rated 2009–2011, the STS beats their 20 mpg average by 1 mpg, about $91 a year. Averaged over the years each was sold, the most economical engine since 2005, the 3.6L 6-cyl (2005–2011), does 19.7 mpg and the thirstiest, the 4.6L 8-cyl (2005–2010), 18: $184 a year apart.
Every Cadillac STS engine, compared
Yearly cost assumes 12,000 miles at $3.20 a gallon.
| Engine | Combined | City / Highway | Years | Fuel per year |
|---|---|---|---|---|
| 3.6L 6-cyl | 16.9 / 25.6 | 2005–2011 | $1,949 | |
| 4.6L 8-cyl | 15 / 23.8 | 2005–2010 | $2,133 |
What that actually costs
Against its rivals in the same model years, the Hyundai Elantra gets 31 mpg, the Nissan Altima 26.9 mpg and the Acura TL 21.7 mpg, next to 21 mpg for the 2011 STS. The STS costs the most of them to run: $590 a year more than the Hyundai Elantra.
| Measure | Value |
|---|---|
| Cost per mile (2011) | $0.152 |
| Fuel per year | $1,829 |
| Fuel over five years | $9,145 |
| Against other V6 cars, 2009–2011 | −$91 a year |
| EPA's own estimate | $3,623 a year |
City or highway — who is this car for
The 2011 Cadillac STS gives up 9 mpg in town: 27 on the highway against 18 in the city, $711 a year if every mile were city driving.
| Measure | Value | Reading |
|---|---|---|
| City (2011) | 18 mpg | $2,133 a year if you only drive in town |
| Highway | 27 mpg | $1,422 a year if you mostly commute |
| Gap | +9 mpg (50%) | Wide — this car dislikes traffic |
How the STS changed over the years
The STS peaked in 2011 at 21 mpg (18 city, 27 highway) and was at its thirstiest in 2005 at 18 — 3 mpg apart, or $304 a year in fuel between buying one year and the other.
| Model year | Combined | City / Highway | Engines offered | Fuel per year |
|---|---|---|---|---|
| 2011 | 18 / 27 | 1 | $1,829 | |
| 2010 | 16.5 / 25.5 | 2 | $1,969 | |
| 2009 | 16 / 25 | 2 | $2,021 | |
| 2008 | 16 / 25 | 2 | $2,021 | |
| 2007 | 15.5 / 24.5 | 2 | $2,076 | |
| 2006 | 15.5 / 24.5 | 2 | $2,076 | |
| 2005 | 15.5 / 23 | 2 | $2,133 |
MPG is a number. Dollars per year is the answer.
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How we count
This page rests on 13 EPA ratings of the Cadillac STS — 2 engines across 2005–2011. 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 $3,623. Full method.
Frequently asked questions
What mpg does the 2011 Cadillac STS get?
21 mpg combined, 18 city and 27 highway, per EPA. Across every year since 2005 the STS has averaged 18.9 mpg.
Is the 2011 STS more efficient than the 2010?
Yes: 21 against 19.5 mpg combined, about $140 a year less to run.
Which STS year has the best gas mileage?
The 2011, at 21 mpg combined (18 city, 27 highway), which is also the latest model year we hold.
Does the STS get better gas mileage than the Hyundai Elantra?
No: 21 mpg for the 2011 STS against 31 for the 2012 Hyundai Elantra, about $590 a year more to run.
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