235mpg? That’s well worth a plug

Toyota’s Prius Plug-In Hybrid has smashed the fuel consumption record in tests. “Our team averaged 83.1mpg, making it easily the most fuel-efficient car we have ever measured,” Which? said.

It said the new Prius, which has a petrol engine and an electric motor, was even more impressive in its urban driving tests. It returned a remarkable 235.4mpg in a simulation of stop-start city driving. Even in a test that simulated out-of-town motoring, it averaged a record-breaking 100.9mpg.

The consumer organisation said this confirmed that it should be “exceptionally frugal in real-world driving scenarios”.

The Prius Plug-In Hybrid’s 83.1mpg figure comfortably beat the previous average fuel economy record set by the Smart ForTwo CDI, which averaged 70.6mpg in Which? tests.

However, the Toyota was not so impressive on the motorway. In a simulated test of motorway driving, the group’s drivers averaged only 46.3mpg.

“This makes the Prius hardly any more frugal than a conventional petrol-engined rival,” Which? said.

“For example, a Mazda6 1.8 petrol would use £15.12 of fuel per 100 motorway miles travelled, compared to the Toyota’s £13.20 of fuel.”

It concluded that the secret to the new car’s exceptional low-speed fuel figures was its battery pack.

Unlike the existing Prius Hybrid, whose electric motor is recharged by the on-board petrol engine alone, the Plug-In Hybrid’s battery can be recharged from a domestic plug socket in 90 minutes.

This gives it a much longer range using electric power only – up to about 14 miles – so the petrol engine is used less.

The cost of recharging the battery from empty at current rates was 64p, making it a cheap car to run in town.

The cost of travelling the same 14 miles in a 1.8 litre Mazda6 would be £2.91.

A spokesman for Toyota said: “The car in a sense represents the next step in terms of hybrid technology.

“We have been selling hybrids since 2000 and this next step delivers the best of both worlds.”

He said this was because the battery power would take drivers 14 miles, meaning it would be sufficient for most short journeys to work and the shops.

However, unlike totally electric cars, there was no need to be dependent on battery-charging infrastructure, with the petrol engine kicking in after 14 miles.

The spokesman told The Scotsman the firm was anticipating the car achieving 134.5mpg, even more than the average experienced by Which? testers.

Which? tested the “lease” version of the car and the retail production version is expected to be lighter, with a more compact battery pack. This, the watchdog agreed, could raise the prospect of even better fuel economy.

The Prius Plug-In Hybrid is due to go on sale in the UK next summer, priced at £31,000. However, as it qualifies for the government’s electric car grant scheme, that is reduced by £5,000 to £26,000.