The Mercedes-Benz 420 does 15 mpg combined (14 city, 17 highway), which works out to about $2,560 a year in fuel at $3.20 a gallon and 12,000 miles. Against other V8 cars it sits below the average of 16.1 mpg.
Every Mercedes-Benz 420 engine, compared
The Mercedes-Benz 420 was rated in a single specification, so its gas mileage does not vary by version — only by model year. Yearly cost assumes 12,000 miles at $3.20 a gallon.
| Engine | Combined | City / Highway | Years | Fuel per year |
|---|---|---|---|---|
| 4.2L 8-cyl | 14 / 17 | 1986–1991 | $2,560 |
What that actually costs
The Mercedes-Benz 420 burns a gallon every 15 miles, so 12,000 miles takes about 800 gallons a year. At $3.20 that is what the table below adds up to.
| Measure | Value |
|---|---|
| Cost per mile | $0.213 |
| Fuel per year | $2,560 |
| Fuel over five years | $12,800 |
| Against other V8 cars | +$175 a year |
| EPA's own estimate | $5,150 a year |
City or highway — who is this car for
The Mercedes-Benz 420 gives up 3 mpg the moment you leave the motorway — 17 out there against 14 in town, a 21% drop worth $484 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 | 14 mpg | $2,743 a year if you only drive in town |
| Highway | 17 mpg | $2,259 a year if you mostly commute |
| Gap | +3 mpg (21%) | Typical for its type |
How the 420 changed over the years
Combined figure across the 6 model years the 420 was rated in, all of them at 15 mpg. 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 |
|---|---|---|---|---|
| 1991 | 14 / 17 | 1 | $2,560 | |
| 1990 | 14 / 17 | 1 | $2,560 | |
| 1989 | 14 / 17 | 1 | $2,560 | |
| 1988 | 14 / 17 | 1 | $2,560 | |
| 1987 | 14 / 17 | 1 | $2,560 | |
| 1986 | 14 / 17 | 1 | $2,560 |
MPG is a number. Dollars per year is the answer.
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How we count
This page rests on 6 EPA ratings of the Mercedes-Benz 420 — 1 engine across 1986–1991. 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 $5,150. Full method.
Frequently asked questions
What mpg does the Mercedes-Benz 420 get?
15 mpg combined on average — 14 in the city and 17 on the highway, per EPA ratings across 1986–1991.
How much does a Mercedes-Benz 420 cost in fuel per year?
About $2,560 at 12,000 miles and $3.20 a gallon — roughly $12,800 over five years, or 0.213 dollars a mile.
Which 420 engine is the most economical?
The 4.2L 8-cyl at 15 mpg.
Is the 420 good on fuel compared with similar cars?
Against other V8 cars it sits below the average of 16.1 mpg, computed across 3323 ratings.
Are these real-world 420 figures?
No — they are EPA laboratory ratings, the same ones printed on the window sticker, and EPA's own annual fuel estimate for the Mercedes-Benz 420 is $5,150 against the $2,560 we compute at 12,000 miles. Expect a little worse in practice: the spread between the city and highway figures is smaller than the spread between two drivers of the same one.
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