New cars are 6.3% less fuel efficient than official figures suggest

This is the latest report in a series of weekly updates for industry colleagues from Rachael Prasher, managing director of What Car? and Haymarket Automotive.

Fuel economy remains a key concern for most buyers, and to help them make the right choice, our True MPG tool shows how economical a new car is under real-world driving conditions.

Our independent laboratory test uses a rolling road to simulate real-world driving styles and is repeatable within one percentage, giving buyers a more accurate estimate of a car’s true fuel economy.

Our latest test batch of 96 vehicles, covering petrol, diesel and hybrid vehicles and everything from small hatchbacks to large SUVs, found that new cars are on average 6.3% less fuel efficient under real-world driving conditions than their manufacturer’s quoted Worldwide Harmonised Light Vehicle Test Procedure (WLTP) figures suggest.

However, our results showed significant differences between vehicles, with some models achieving 25% less than their manufacturers quoted, while others proved significantly more economical than official tests show. Those that underperformed included BMW’s 420d M Sport Pro Edition, which was found to achieve 26.4% lower fuel economy than its official WLTP test results declared, and the Suzuki Swace 1.8 Hybrid, which was 21.6% less economical than its maker quotes.

At the other end of the spectrum, the Ford Ranger 2.0 Diesel, was found to achieve 18.9% better fuel economy under real-world driving conditions, while the Honda CR-V Hybrid 2.0 i- MMD performed 12.3% better than it did under WLTP testing.

Though the WLTP results have proven to be more accurate than previous industry standards were, our research shows just how much fuel economy varies between different models. This is why test drives, especially extended ones, remain important for customers, as it will give them the most accurate view of how efficient a car is likely to be with them behind the wheel.

Top 10 True MPG under-achievers

RankModel Average True MPGWLTP combinedShortfall over WLTP
1BMW 420d 2.0 diesel M Sport Pro Edition42.457.626.4%
2Suzuki Swace 1.8 Hybrid SZT 50.364.221.6%
3Ford Fiesta 1.0 155 petrol ST-Line X Edition42.753.319.9%
4Renault Clio 1.6 petrol hybrid 140 Iconic E-Tech51.664.219.6%
5Audi A3 Saloon 1.5 35 TFSI 150 petrol S Line40.948.716.0%
6BMW M340i Touring 3.0 M340i M Sport28.033.215.7%
7Audi Q2 1.5 35 TFSI petrol S Line38.545.615.6%
8Ford Focus 2.3 Ecoboost ST29.634.915.2%
9BMW 118i M Sport36.342.815.2%
10Hyundai i20 1.0 petrol T-GDi SE Connect47.855.413.7%

Top 10 True MPG over-achievers

RankModelAverage True MPGWLTP combinedImprovement over WLTP 
1Ford Ranger 2.0 diesel Thunder36.530.718.9%
2Honda CR-V Hybrid 2.0 i-MMD SR47.442.212.3%
3Volkswagen Up 1.0 S/S 60PS R-Line56.050.710.5%
4Dacia Duster 1.3 TCe 130 Comfort43.839.810.1%
5Honda Civic Type R 2.0 VTEC Turbo GT36.333.29.2%
6Skoda Karoq 1.5 TSI SE L44.240.59.1%
7Suzuki Ignis K12D 1.2 Dualjet Hybrid SZT 2W59.955.77.5%
8Toyota GR Yaris 1.6 petrol Non-Circuit Pack35.934.34.5%
9Lexus LC500 Cabriolet 5.0 V8 Sport Plus Pack24.224.10.5%
10Kia Sorento 2.2 CRDi diesel 342.342.20.3%

For further insight from whatcar.com’s unique website data, please contact claire.groves@haymarket.com