Diesel v hybrid cars: which goes further?

New research has added weight to arguments about the inefficiency of hybrid cars for longer journeys when compared with diesels. A British emissions-research company has been analysing the fuel-performance figures of 10 popular cars – eight diesel and two hybrid – and, predictably, finds that diesels are better on longer journeys but hybrids are best in city driving conditions.

Emissions Analytics tested a 1.6 Honda Civic diesel, a Skoda Octavia 1.6 diesel, a Peugeot 308 diesel, a Mazda 3 2.3 diesel, a Toyota Auris 1.8 petrol hybrid, a Citroën C4 Cactus 1.6 diesel, a Toyota Yaris 1.5 petrol hybrid, a Peugeot 2008 1.5 diesel, a Volkswagen Golf 1.6 Bluemotion diesel, and a Honda CRV 1.6 diesel.

The company says the common perception that hybrids have an advantage over frugal diesel engines is “often illusory” if judged solely on fuel economy. Hybrids delivered good fuel economy in real driving conditions, but they could be eclipsed by better consumption in some standard diesels.

The analysis showed that urban congestion added 6 per cent to diesel consumption figures; 2.5 per cent to diesel-hybrid figures; 8.3 per cent to petrol figures and 3.3 per cent to petrol-hybrid figures.

When driven on motorways, however, the standard diesel offered 18.4 per cent better figures, diesel hybrid only 1.1 per cent, petrol 27.4 per cent and petrol hybrid 8.5 per cent.

These statistics are based on a data set of 500 vehicles being driven on British roads in association with What Car?

Emissions Analytics says the data shows hybrids suffer much less than the others cars in congested conditions, but when the acceleration rate is doubled then fuel consumption falls by more for hybrids, especially diesels.

When comparing city driving to motorway conditions, all the cars had better performance but the smaller engines in the hybrids were far less suited to motorways.

The company says hybrids deliver good but not best-in- class consumption, but they are typically the cleanest, and if “you are a light-footed congested-town driver they are ideal”.

Petrol hybrids also had the benefit of less impact on air quality, and this improved even more in city conditions, when more battery power was used. Plug-in hybrids showed this pattern even more strongly.