BMW 640i Convertible
23 MPG The 2018 BMW 640i Convertible is EPA-rated at 23 MPG combined (20 city / 29 highway). Over 15,000 miles a year that is about 652 gallons, $2087 a year in fuel, or $0.139 per mile at $3.20/gal.
Across its full 2012–2018 run it averages 23.3 MPG, essentially flat across 7 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 | $0.109 | $1087 | $1630 | $2174 |
| $3.00/gal | $0.130 | $1304 | $1957 | $2609 |
| $3.20/gal | $0.139 | $1391 | $2087 | $2783 |
| $3.50/gal | $0.152 | $1522 | $2283 | $3043 |
| $4.00/gal | $0.174 | $1739 | $2609 | $3478 |
| $4.50/gal | $0.196 | $1957 | $2935 | $3913 |
| $5.00/gal | $0.217 | $2174 | $3261 | $4348 |
Every model year
| Year | Combined | City | Highway | EPA fuel cost/yr | CO₂ g/mi | Trims |
|---|---|---|---|---|---|---|
| 2018 | 23 MPG | 20 | 29 | $3350 | 378 | 1 |
| 2017 | 23 MPG | 20 | 29 | $3350 | 377 | 1 |
| 2016 | 23 MPG | 20 | 30 | $3350 | 378 | 1 |
| 2015 | 24 MPG | 20 | 30 | $3200 | 376 | 1 |
| 2014 | 23 MPG | 20 | 30 | $3350 | 378 | 1 |
| 2013 | 24 MPG | 20 | 30 | $3200 | 375 | 1 |
| 2012 | 23 MPG | 20 | 30 | $3350 | 386 | 1 |
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 229 subcompact cars models tracked here, the BMW 640i Convertible ranks 103 on current figures, against a class average of 24.2 MPG.
Closest more-efficient alternatives in the same class: BMW 318i/318is (23.5), Nissan Pulsar NX (23.5), Subaru Hatchback (23.5), Volkswagen Cabrio (23.5), BMW 230i xDrive Convertible (24).
Tailpipe CO₂ is rated at 378 grams per mile, which works out to roughly 5.7 tonnes a year at 15,000 miles.
Questions
What MPG does the BMW 640i Convertible get?
The 2018 BMW 640i Convertible is rated at 23 MPG combined by the EPA — 20 city and 29 highway. Across all 7 model years in the database it averages 23.3 MPG, ranging from 23 to 24 depending on year and trim.
How much does a BMW 640i Convertible cost in fuel per year?
At 23 MPG and 15,000 miles a year, it burns about 652 gallons — roughly $2087 a year with fuel at $3.20 a gallon, or $0.139 per mile. The EPA's own published annual figure for the 2018 model is $3350.
Has the BMW 640i Convertible become more efficient over time?
Barely. It sits at 23 MPG today against 23 in 2012 — essentially flat across 7 model years, with efficiency gains offset by weight and power creep.
Is the BMW 640i Convertible efficient for its class?
It ranks 103 of 229 in the Subcompact Cars class on current figures, against a class average of 24.2 MPG. That is 1.2 worse 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.