Mazda3 review - MPG, running costs & CO2

Mazda has a proud history of ‘doing things differently’ when it comes to engine technology. In recent years, the brand has shunned the trend for 'downsizing' for its petrol and diesel engines, instead saying it "rightsizes" its models. The Mazda3 launched with an already-large 2.0-litre entry-level petrol engine, but has since discontinued this in favour of an even-larger 2.5-litre unit, while the higher-performance e-Skyactiv X 2.0-litre engine still remains.

Despite the engine size, economy doesn’t suffer because Mazda's e-SkyActiv X petrol uses a clever ignition system that blends high-pressure diesel engine technology with conventional petrol attributes to deliver impressive driveability and running costs. If you can afford it, it's our pick of the range, and it’s even more economical on paper than the less-powerful 2.5-litre. 

Mazda3 MPG & CO2

All versions of the Mazda3 now sport mild-hybrid technology and the ability to shut off individual cylinders to save fuel under light throttle. As of 2024, the less-powerful 2.0-litre e-SkyActiv G engine has been discontinued in favour of a larger 2.5-litre version. An extra bump up in power has come at the expense of some fuel economy, but it’s still very efficient, capable of up to 47.9mpg. CO2 emissions stand at around 133g/km, so it won’t be the cheapest choice for company car buyers.

Go for the smaller, yet more-powerful 2.0-litre e-SkyActiv X engine and you’ll get a better on-paper fuel economy figure of up to 51.4mpg and lower CO2 emissions of 123g/km. It’s more expensive, though, and available only on mid-spec Centre-Line trim at almost £2,000 more than the 2.5-litre car.

The 1.8-litre SkyActiv-D diesel engine was discontinued in 2019. This engine produced 56.6mpg under the WLTP testing cycle and CO2 emissions of 107g/km when equipped with a six-speed manual gearbox. With an automatic gearbox, the diesel managed around 50mpg, while CO2 emissions also increased to 127g/km.

Insurance groups

Insurance groups for the latest Mazda3 e-SkyActiv G petrol start from 16 in Prime-Line trim and go up to 22 for an Exclusive-Line range-topper.

Warranty

Mazda offers a three-year, 60,000-mile warranty, which puts it on an equal footing with rivals from Ford and Volkswagen. It looks a bit stingy next to Hyundai's five-year/unlimited mileage offer and Kia's seven-year/100,000-mile warranty, however.