Comparing gearboxes across the market is meaningless — ten-speeds go in big trucks and four-speeds went in small cars. So I held the engine constant: four cylinders, 2.0 to 2.5 litres, conventional automatics only, CVTs excluded.
| Gears | Combined mpg | |
|---|---|---|
| 4-speed | 21.2 | |
| 5-speed | 22.4 | |
| 6-speed | 25.6 | |
| 7-speed | 26.3 | Peak |
| 8-speed | 25.4 | |
| 9-speed | 23.9 | |
| 10-speed | 23.0 | Below a 6-speed |
The gains were real until they weren't
Four to six speeds bought 4.4 mpg — a genuine, large improvement. Six to seven added another 0.7.
After that it reverses. Eight speeds gives back 0.9, nine gives back 2.4, and a ten-speed lands at 23.0 mpg — worse than the six-speed it replaced.
The running cost follows: a six-speed averages $2,615 a year in fuel, a nine-speed $3,052.
Why more gears stop paying
The point of extra ratios is keeping the engine near its efficient band. Past a certain count the band is already covered, and each additional gear adds cost without adding coverage.
Meanwhile the drawbacks accumulate. More gearsets mean more rotating mass and more parasitic drag. More shifts mean more time in transition rather than in gear. And a gearbox constantly hunting between closely spaced ratios spends its life shifting — which is why owners of nine and ten-speed cars often describe them as busy or indecisive.
There's also a marketing element that has nothing to do with efficiency: gear count is a specification that looks like progress on a brochure.
The average kept climbing anyway
Automatics averaged 3.39 gears in the late eighties and 8.34 in 2025 — the maximum went from four to ten.
And a different transmission has quietly overtaken all of them. The single most common configuration in the EPA database is now the one-speed reduction gear of an electric car, which appears in 1,367 records across 42 brands. Its share of the model range went from 1.6% in 2015 to 26.1% in 2026. After decades of adding ratios, the fastest-growing transmission has none.
What this means when buying
Don't pay for gear count. Between two versions of the same car, the one with more ratios is not the more economical one past seven.
Consider the repair side. A nine or ten-speed automatic is a complex unit, and rebuild costs scale with complexity. On a high-mileage used car that's a real exposure.
Test drive for hunting. If the gearbox shifts constantly at moderate speeds, that's the behaviour the numbers describe, and it doesn't improve with familiarity.
Check what's actually fitted. Transmission is missing from 30% of used listings. A VIN check decodes the gearbox and engine the car was built with. We compared the two transmission types in the automatic is more economical than the manual.
Frequently asked questions
Do more gears mean better fuel economy?
Only up to seven. At matched displacement, seven-speed automatics peak at 26.3 mpg, then economy falls: 25.4 for eight speeds, 23.9 for nine and 23.0 for ten — below the 25.6 of a six-speed.
Why do ten-speed gearboxes perform worse?
Past a certain count the extra ratios don't extend the engine's efficient band but do add rotating mass, parasitic drag and time spent shifting rather than driving. The gearbox also hunts between closely spaced ratios.
How many gears does a modern automatic have?
An average of 8.34 in 2025, up from 3.39 in the late 1980s. But the fastest-growing transmission is the one-speed reduction gear in electric cars, which went from 1.6% of the model range in 2015 to 26.1% in 2026.
Should I avoid a nine or ten-speed automatic?
It's not a dealbreaker, but don't pay a premium for the gear count. They're more complex to rebuild on a high-mileage car, and if the gearbox hunts noticeably on a test drive, that behaviour won't improve.
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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