Comparing petrol cars within the same EPA class and model year — so a compact competes with compacts — and sorting by combined economy.
| Combined mpg | Relative price | Median price |
|---|---|---|
| Under 20 | 1.855 | $12,031 |
| 20–23 | 1.203 | $9,244 |
| 24–27 | 1.094 | $7,999 |
| 28–31 | 0.892 | $6,714 |
| 32 and over | 0.816 | $7,720 |
Every step up in economy costs residual value
The gradient is clean and monotonic. A saloon returning under 20 mpg sells at 1.855 of its class average. The same size car returning 32-plus sells at 0.816 — a 2.27x spread on vehicles competing in the same segment.
Why the market pays for thirst
Fuel economy inside a class is a proxy for engine size, and engine size is a proxy for equipment level. The sub-20 mpg midsize saloon isn't a base model — it's the V6 or the performance version, with the leather, the bigger wheels and the higher original sticker.
The 32-plus car in the same class is the four-cylinder economy trim, which started cheaper and stayed cheaper.
So the market isn't rewarding inefficiency. It's pricing what came with the engine.
But the fuel cost doesn't come back
That's the part worth sitting with. The economical car costs less to buy and less to run, and it still loses more value proportionally. Its cheapness is not compensated at resale — the discount you enjoyed at purchase is the discount the next buyer will demand.
Meanwhile the thirsty version holds its position while costing roughly $900 per pair of cylinders per year to fuel.
And the economical ones get driven harder
Normalised against class and year, the pattern reverses on the odometer: cars under 18 mpg show relative mileage of 0.978 while cars over 35 mpg show 1.073. Cheaper miles mean more miles.
In raw numbers it looks opposite — 140,676 miles on thirsty cars against 113,611 on economical ones — but that's the class effect, since big engines go in vehicles kept longer. Compare like with like and the efficient car has worked harder.
What to do with this
If you're buying to keep, economy still wins. Lower purchase price plus lower running costs beats a residual you only realise on sale.
If you're buying to resell in two years, the maths inverts. The efficient car will give back more of its value proportionally.
Expect higher mileage on economical examples. They're driven more within their class, so the odometer will run ahead of comparable thirsty cars.
Check the exact engine. Within one model year the spread across powertrains can exceed 18 mpg, and it decides which side of this table the car sits on. A VIN check decodes what it was built with.
Frequently asked questions
Do fuel-efficient cars hold their value?
Worse than thirsty ones. Within the same EPA class, petrol cars under 20 mpg price at 1.855 of their segment average while cars over 32 mpg sit at 0.816 — a 2.27x gap.
Why do thirsty cars sell for more?
Inside a class, low economy is a proxy for a larger engine, and a larger engine means a higher trim — leather, bigger wheels, a higher original price. The market is pricing what came with the engine, not the thirst itself.
Do economical cars get driven more?
Yes, once you control for class and year. Cars under 18 mpg show relative mileage of 0.978 against 1.073 for cars over 35 mpg — cheaper miles mean more miles.
Should I still buy an economical car?
If you're keeping it, yes — lower purchase price and lower running costs outweigh a residual you only realise on sale. If you plan to resell within a couple of years, the efficient car gives back proportionally more of its value.
Denis Kataev is a serial solopreneur and the founder of ForCar. With 15+ years in software engineering and 10 years in SEO, he builds data-driven products end to end — backed by a sharp eye for design. At ForCar he mines proprietary vehicle datasets, turning raw numbers into buying advice you can actually trust.
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