The BMW M340i does 26.7 mpg combined (24 city, 31.7 highway), which works out to about $1,438 a year in fuel at $3.20 a gallon and 12,000 miles. Engine choice matters more than you'd think: 3L 4-cyl Hybrid does 29 mpg while 3L 6-cyl does 25 — a difference of $212 a year. Against other Hybrid cars it sits below the average of 29.8 mpg.
Every BMW M340i engine, compared
Gas mileage on the BMW M340i ranges from 29 down to 25 depending on which engine sits under the bonnet — a spread of $212 a year across 3 versions of the same car. Picking the right one often saves more fuel than picking a different car altogether. Yearly cost assumes 12,000 miles at $3.20 a gallon.
| Engine | Combined | City / Highway | Years | Fuel per year |
|---|---|---|---|---|
| 3L 4-cyl Hybrid | 27 / 33 | 2025–2025 | $1,324 | |
| 3L 6-cyl Hybrid | 23.8 / 31.8 | 2021–2026 | $1,444 | |
| 3L 6-cyl | 22 / 30 | 2020–2020 | $1,536 |
What that actually costs
The BMW M340i burns a gallon every 26.7 miles, so 12,000 miles takes about 449 gallons a year. At $3.20 that is what the table below adds up to.
| Measure | Value |
|---|---|
| Cost per mile | $0.120 |
| Fuel per year | $1,438 |
| Fuel over five years | $7,190 |
| Against other Hybrid cars | +$149 a year |
| EPA's own estimate | $2,886 a year |
City or highway — who is this car for
The BMW M340i gives up 7.7 mpg the moment you leave the motorway — 31.7 out there against 24 in town, a 32% drop worth $389 a year. A wide gap punishes stop-and-start traffic; a narrow one means the car doesn't care where you drive it.
| Measure | Value | Reading |
|---|---|---|
| City | 24 mpg | $1,600 a year if you only drive in town |
| Highway | 31.7 mpg | $1,211 a year if you mostly commute |
| Gap | +7.7 mpg (32%) | Wide — this car dislikes traffic |
How the M340i changed over the years
The M340i peaked in 2026 at 29 mpg (27 city, 33 highway) and was at its thirstiest in 2020 at 25 — 4 mpg apart, or $212 a year in fuel between buying one year and the other. The 2026 car does 29. Jumps usually mark a new generation or a new engine; dips often mean a heavier body or added all-wheel drive.
| Model year | Combined | City / Highway | Engines offered | Fuel per year |
|---|---|---|---|---|
| 2026 | 27 / 33 | 1 | $1,324 | |
| 2025 | 27 / 33 | 1 | $1,324 | |
| 2024 | 23 / 31 | 1 | $1,477 | |
| 2023 | 23 / 31 | 1 | $1,477 | |
| 2022 | 23 / 32 | 1 | $1,477 | |
| 2021 | 23 / 32 | 1 | $1,477 | |
| 2020 | 22 / 30 | 1 | $1,536 |
MPG is a number. Dollars per year is the answer.
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How we count
This page rests on 7 EPA ratings of the BMW M340i — 3 engines across 2020–2026. 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 $2,886. Full method.
Frequently asked questions
What mpg does the BMW M340i get?
26.7 mpg combined on average — 24 in the city and 31.7 on the highway, per EPA ratings across 2020–2026.
How much does a BMW M340i cost in fuel per year?
About $1,438 at 12,000 miles and $3.20 a gallon — roughly $7,190 over five years, or 0.120 dollars a mile.
Which M340i engine is the most economical?
The 3L 4-cyl Hybrid at 29 mpg, against 25 for the 3L 6-cyl — a difference of about $212 a year.
Is the M340i good on fuel compared with similar cars?
Against other Hybrid cars it sits below the average of 29.8 mpg, computed across 1162 ratings.
Are these real-world M340i figures?
No — they are EPA laboratory ratings, the same ones printed on the window sticker, and EPA's own annual fuel estimate for the BMW M340i is $2,886 against the $1,438 we compute at 12,000 miles. Expect a little worse in practice: the spread between the 29 and 25 mpg versions of this car is smaller than the spread between two drivers of the same one.
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