The BMW 645Ci does 19.0 mpg combined (16.0 city, 24.0 highway), which works out to about $2,021 a year in fuel at $3.20 a gallon and 12,000 miles. Against other V8 cars it sits above the average of 15.6 mpg.
Every BMW 645Ci engine, compared
Picking the right version of the same car 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 |
|---|---|---|---|---|
| 4.4L 8-cyl | 16 / 24 | 2004–2005 | $2,021 |
What that actually costs
Miles per gallon is an abstraction; the fuel bill is not. Here it is in money, at 12,000 miles a year and $3.20 a gallon.
| Measure | Value |
|---|---|
| Cost per mile | $0.168 |
| Fuel per year | $2,021 |
| Fuel over five years | $10,105 |
| Against other V8 cars | −$441 a year |
| EPA's own estimate | $3,900 a year |
City or highway — who is this car for
The gap between city and highway figures tells you whom the car suits. 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 | 16.0 mpg | $2,400 a year if you only drive in town |
| Highway | 24.0 mpg | $1,600 a year if you mostly commute |
| Gap | +8 mpg (50%) | Wide — this car dislikes traffic |
How the 645Ci changed over the years
Combined figure by model year. 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 |
|---|---|---|---|---|
| 2005 | 16 / 24 | 1 | $2,021 | |
| 2004 | 16 / 24 | 1 | $2,021 |
MPG is a number. Dollars per year is the answer.
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How we count
Fuel-economy figures come from EPA fueleconomy.gov — the same laboratory numbers printed on the window sticker. We don't adjust them; real-world consumption depends on how and where you drive.
What we add is money. Yearly cost assumes 12,000 miles at $3.20 a gallon — change either and the ranking stays, only the size of the bill moves. Cost per mile is the same figure divided out, useful when comparing a commute against a weekend car.
Frequently asked questions
What mpg does the BMW 645Ci get?
19.0 mpg combined on average — 16.0 in the city and 24.0 on the highway, per EPA ratings across 2004–2005.
How much does a BMW 645Ci cost in fuel per year?
About $2,021 at 12,000 miles and $3.20 a gallon — roughly $10,105 over five years, or 0.168 dollars a mile.
Which 645Ci engine is the most economical?
The 4.4L 8-cyl at 19 mpg.
Is the 645Ci good on fuel compared with similar cars?
Against other V8 cars it sits above the average of 15.6 mpg, computed across 4665 ratings.
Are these real-world figures?
No — they are EPA laboratory ratings, the same ones on the window sticker. Real consumption depends on driving style, terrain, load and weather, and is typically a little worse.