In-depth Reviews

BMW 3 Series saloon - MPG, running costs & CO2

BMW 3 Series petrol and diesel engines are economical, and the 330e hybrid is even better

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4.4 out of 5

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3.4 out of 5

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MPG, running costs & CO2 Rating

4.5 out of 5

The latest BMW 3 Series comes at a time when diesel power has rather lost its sheen. Despite this, the BMW's conventional petrol and diesel engines are some of the best in the business, and there's also a plug-in hybrid alternative.

Whichever version you choose, you can take comfort in the knowledge that the latest thinking in aerodynamics – including features such as an active front grille to manage airflow – has gone into making sure the 3 Series is impressively fuel-efficient.

BMW 3 Series MPG & CO2

In recent years, the 320d diesel has proven by far the most popular 3 Series model, thanks to its impressive blend of performance and fuel economy. The latest version is claimed to return up to 60.1mpg in its most efficient form, with CO2 emissions of 123-131g/km for SE models rising to 130-139g/km for those equipped with xDrive four-wheel drive. The latter results in a mid-range Benefit-in-Kind (BiK) company car tax rating, with higher trims and larger wheels resulting in higher running costs. If its fuel-efficiency appears lower than older versions, that's because it's the first 3 Series to undergo stricter WLTP testing, producing results that should be closer to real-world driving.

There's also a 318d that returns economy figures similar to the 320d, with SE spec cars capable of up to 58.9mpg when equipped with smaller alloy wheels. It’s also worth noting the four-wheel drive 320d xDrive models are slightly less fuel efficient than their rear-wheel drive counterparts, with claimed economy dropping to 57.6mpg for the automatic gearbox versions (the xDrive cannot be ordered with a manual transmission). A powerful BMW 330d returns up to 49.6mpg and emits 150-159g/km, making it costlier for company-car drivers.

The 318i and 320i models officially manage up 44.1mpg, although we struggled to better 33mpg during our time with the latter car. Both are also slightly cheaper options for business drivers compared with a diesel model, with CO2 emissions of 145-154g/km. The 330i uses a turbocharged 2.0-litre, four-cylinder petrol engine that produces 254bhp. It's claimed to return up to 42.8mpg, with CO2 emissions of 150-158g/km placing it towards the top of the BiK bandings. With 369bhp, the BMW 340i xDrive prioritises performance over fuel-efficiency, but still manages to return up to 34.9mpg with emissions of 185-189g/km.

The BMW 330e plug-in hybrid is the most efficient in the range. Its battery pack provides an all-electric driving range of up to 37 miles when fully charged, helping the car achieve a low emissions figure of 30-34g/km and fuel economy of 217.3mpg - although you may struggle to achieve this number unless you use the electric power for most journeys. This qualifies for the lowest BIK rate for business drivers, and also makes it exempt from emissions tariffs like the London Congestion Charge.

If you manage to keep the price of your 3 Series below £40,000, you'll be liable for a £150 road tax bill from the second year - the first year’s tax will be bundled into the price. Break that price barrier and you'll need to pay an additional £325 surcharge on the first five occasions that you pay road tax, bringing the total to £475 a year.


The BMW 3 Series is an upmarket car but the insurance groups are fairly reasonable. Kicking off the range is the 318d in SE trim, which occupies group 25 out of 50. The 320d starts in group 28 and spans up to 32 for the 320d xDrive M Sport Plus Edition, and the 330d covers groups 38 and 39. Petrol models start in 28 (a 320i xDrive in SE spec), while the powerful 330i and 330e versions occupy groups 32 and 33 respectively. The most potent model, the M340i xDrive, sits in group 38.


Like all BMWs, the 3 Series uses sensors and oil-quality monitors to determine when routine maintenance is required. Typically, visits to the workshop will be called for between one and two years apart, with fewer than 20,000 miles elapsing between services. Certain components, such as spark plugs on petrol engines, and fuel and air filters, will need occasional replacement, and a service contract will enable you to budget for these items more easily. Your BMW dealer will be able to arrange a contract to match your driving requirements.


BMW provides all new car buyers with a three-year, unlimited mileage warranty, which includes three years of BMW Emergency Service cover. It compares directly to the policy Mercedes gives its customers and beats Audi's warranty by having no mileage limit. At the end of your warranty, it can be followed up by a 'BMW Insured Warranty' on a year-by-year basis, although there are certain exclusions under such policies.

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