The price of oil hit the headlines again last week, prompting worried discussion over whether petrol prices are about to rise. On hearing that ominous news, car buyers inevitably begin to pay more attention to the very small print at the bottom of advertisements for new vehicles: the fuel consumption figures.
Flip through car magazines and adverts and you could be forgiven for thinking that somebody wanting to buy a new vehicle that is as efficient as possible should look at just one type of car: the high-tech, clean, green and super-economical hybrid.
These cars combine electric and petrol engines to increase efficiency and thus reduce pollution. The battery supplies additional power when needed, meaning the conventional engine can be much smaller and more frugal. When the cars slow down, their energy is captured in dynamos that recharge the battery, rather than being wasted simply heating brake pads.
In America the cars have been hailed as the future of motoring and their appeal has been boosted by celebrities driving them to underline their green credentials. Here they are exempt from the London congestion charge in recognition of their cleanliness and efficiency.
Surely, then, the hybrid is the automatic choice for economy? Well, not necessarily. Since official fuel consumption figures are measured on rolling roads in laboratories and often differ wildly from the real world, we decided to test four cars over 200 miles on real roads. The results showed the headline-grabbing hybrid being eclipsed by the humble — and it must be said, far cheaper — diesel.
Advertisement
We took the two leading hybrids: the Honda Civic IMA (£15,013) and the Toyota Prius, with prices ranging from £17,545 to £20,045. (The only other hybrid on the market, the Honda Insight, sold just three units in Britain last year.) Against them we pitched the new Vauxhall Astra CDTi SRi, powered by a 100bhp, 1.7 litre diesel and costing £16,095, and Citroën’s C3 1.4 HDI SX (£11,945). All are five-door hatchbacks, except the Civic IMA, which is a saloon. Conventional petrol cars were not tested as they would have struggled to come close.
The cars were driven from London to Chichester, on the south coast, and back on a route designed to incorporate the three different driving environments we routinely face: town, mixed country roads and the motorway. The majority of the miles were completed on motorways, but thanks to the glacial speed of London traffic we spent more time in town.
Measuring clear dual carriageway as motorway, this incorporated 19 miles of town driving, 44 miles of country roads and 139 miles of motorway. All four cars travelled in a convoy. The fuel economy figures for each section were recorded from the vehicles’ onboard computers.
The interesting part of the journey was calculating the results. Over our mixed course, the clear winner was not a hybrid but a diesel. The Citroën C3 managed an impressive 59mpg overall, significantly beating the two hybrids. The diesel Astra, which was more powerful than the other three cars, came in last overall, proving it is not simply a case of all diesels beating hybrids but that each car needs to be considered on its merits.
Crucially, the test showed that to buy the most efficient car you must work out what type of motoring you do most. Stop-start town traffic gave an advantage to the hybrids, with the Prius, which can run solely on its electric motor at slow speeds, far in the lead. By contrast, motorway miles favoured the diesels, with the C3 way ahead of the hybrids, and the Astra, which had been 21mpg off the Prius in town, coming within 4mpg of it.
Advertisement
Hybrids have other advantages, such as fewer particulate and carbon dioxide emissions and company-car tax benefits, yet on economy alone it seems the modest diesels are still in the running.