The case for the turbo is that it lets a 1.5-litre do the job of a 2.5, so you burn less fuel. That comparison is always made against a bigger engine. I made it against the same one.
| Displacement | Turbo | Naturally aspirated |
|---|---|---|
| 1.5 litre | 29.9 | 37.1 |
| 1.6 litre | 29.4 | 37.1 |
| 1.8 litre | 27.4 | 35.7 |
| 2.0 litre | 25.2 | 31.8 |
| 2.5 litre | 23.6 | 30.0 |
Six to eight mpg, every bracket
Four-cylinder engines, 2015 onwards, superchargers excluded. The turbo loses in all five displacement brackets, by 6.4 to 8.3 mpg.
The obvious objection is that turbo engines go into heavier or sportier cars. So I controlled for that too, comparing inside single EPA vehicle classes at 1.9–2.1 litres: compacts 26.4 against 32.7, midsize 26.0 against 35.3, large cars 25.4 against 39.9. The gap holds in eight classes out of nine.
Why the promise doesn't hold up
The efficiency argument is real but conditional. A small turbo engine is efficient at light load, cruising, off boost. The moment you ask for the power the turbo exists to provide, it burns fuel like the larger engine it replaced — because at that point it is producing what the larger engine produced.
The EPA test cycle is gentle, which is why turbos rate as well as they do. Real driving is less gentle, which is why owners routinely report worse figures than the sticker on a turbo car and roughly the sticker on an atmospheric one.
The comparison the industry makes is against the engine you would have bought in 2005. The comparison a buyer needs is against the engine sitting next to it on the forecourt today.
And then there's the fuel grade
Here is the part that turns an mpg argument into a money one. 69.6% of turbo engines require premium petrol, against 30.1% of naturally aspirated ones.
Put together: the average turbo is 2.72 litres and costs $3,319 a year to fuel. The average naturally aspirated engine is 3.57 litres — nearly a litre bigger — and costs $3,128. Downsizing moved the cost from displacement to octane, and the owner ends up $191 a year worse off with a smaller engine.
What to do about it
Check the fuel grade before the mpg figure. A premium requirement adds roughly $500 a year at typical mileage and never appears in an economy comparison.
Turbos now dominate, so this is a used-market question. Their share went from 6.5% in the late eighties to 54.6% in 2020–24 — on a modern car the turbo is usually the only option, but on a five-to-ten-year-old one you can often still choose.
Confirm which engine the specific car has. A single model year can carry ratings 18 mpg apart, as we found in two 2025 Civics can differ by 18 mpg. The engine is encoded in the VIN, and a VIN check decodes it — listings state the wrong powertrain constantly.
We priced what each cylinder costs annually in each pair of cylinders adds $900 a year.
Frequently asked questions
Are turbo engines more fuel efficient?
Not at the same displacement. A 1.5-litre turbo returns 29.9 mpg against 37.1 for the naturally aspirated version, and the gap of 6–8 mpg holds across every bracket and in eight vehicle classes out of nine.
Why do turbo engines rate well on the EPA test then?
A small turbo is efficient at light load, which is what the test cycle measures. Under real acceleration it burns fuel like the larger engine it replaced, because at that point it's producing the same power.
Do turbo engines need premium fuel?
Most do — 69.6% of turbocharged engines require premium against 30.1% of naturally aspirated ones. That's why the average turbo costs $3,319 a year to fuel against $3,128 for an atmospheric engine nearly a litre larger.
Can I still buy a naturally aspirated car?
On the used market, often yes. Turbo share rose from 6.5% in the late 1980s to 54.6% in 2020–24, so on a modern car it's usually the only option — but on a five-to-ten-year-old vehicle both versions are typically available.
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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