The EPA measures two things about what leaves the exhaust: carbon dioxide per mile, which is about fuel burned, and a smog rating from 1 to 10, which is about the stuff that affects the air you breathe — nitrogen oxides and particulates.
I averaged both across every model rated from 2020 onwards, by brand.
| Brand | CO₂ per mile | Smog rating /10 |
|---|---|---|
| Lamborghini | 1.5 | |
| Rolls-Royce | 2.8 | |
| Ferrari | 3.8 | |
| Aston Martin | 3.7 | |
| Hyundai | 5.8 | |
| Mitsubishi | 5.2 | |
| Volvo | 6.2 |
645 grams against 292. Drive a Lamborghini a mile and you've put out what a Volvo manages in 2.2.
The smog column is the one to read
CO₂ is straightforward — it tracks fuel consumption, so a thirsty car emits more, and nobody is surprised.
The smog rating is different and more interesting. It measures the emissions that cause immediate local harm rather than long-term warming, and it's scored on a curve where 10 is cleanest. Lamborghini's 1.5 is close to the floor.
What makes that notable is that it isn't only about size. A modern engine can be large and still clean if it's engineered for emissions — plenty of full-size trucks score respectably. Scoring 1.5 takes a particular combination: high-revving, high-output engines tuned for power delivery, produced in volumes too small to justify the aftertreatment development that mainstream manufacturers amortise across millions of cars.
Volvo at the top is the real story
Volvo isn't a small-car brand. It sells mostly SUVs and estates, and yet it posts the lowest average CO₂ and the best smog rating in the table.
That's the plug-in hybrid strategy showing up in the data. When a large share of your line-up can run on electricity for the first thirty or forty miles, the fleet average drops sharply even though every individual car is still a two-tonne SUV. Hyundai and Mitsubishi are on the same list for the same reason.
It's a useful reminder that badge assumptions are unreliable. "Swedish estate" doesn't sound cleaner than "Japanese hatchback", but the powertrain decides, not the shape.
What this means if you're buying
For most people the smog rating is the number worth looking up, because it's the one that varies most between cars that look similar on paper — and in states with emissions testing it's the one that determines whether a car passes.
Both figures are on the original window sticker, which you can pull by VIN for any car including a used one. That's more reliable than a spec sheet, because it reflects the exact engine and trim the car left the factory with rather than the best figure in the range.
And keep the running-cost side in view: the same engines that score badly here are the ones that cost $8,012 more in fuel over five years because they require premium. The emissions figure and the fuel bill are two views of the same fact.
Frequently asked questions
Which car brand emits the most CO₂?
Lamborghini, at an average of 645 grams per mile across models rated since 2020, followed by Rolls-Royce (625 g) and Ferrari (533 g). Volvo is lowest at 292 g.
What is the EPA smog rating?
A 1-to-10 score for emissions that cause local air pollution — nitrogen oxides and particulates — rather than CO₂. Ten is cleanest. Lamborghini averages 1.5; Volvo 6.2.
Why does Volvo score best despite selling large SUVs?
Plug-in hybrids. When much of the line-up runs on electricity for the first thirty to forty miles, the brand average drops sharply even though the individual vehicles are heavy. Hyundai and Mitsubishi appear near the top for the same reason.
Where do I find these figures for a specific car?
On the original window sticker, which lists both CO₂ per mile and the smog rating for the exact engine and trim. You can pull it by VIN even for a used car whose paperwork is long gone.
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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