Honda, which long resisted making diesel engines, plans to introduce a range of small capacity turbodiesel engines based on the new 1.6-litre i-DTEC unit which will become available in the Civic at the start of 2013.

The Japanese company was late to the diesel segment popular in Europe and did not introduce its first in-house-developed engine – an I4 2.2 – until as late as 2003. That engine has since been re-developed and now appears in a number of Hondas, including the Civic. Honda had earlier bought-in a PSA engine for a Civic model line it shared with Rover Group from the late ’80s.

But with small capacity diesels now claiming 58% of the European market for Civic-sized cars, something smaller was required.

“The mainstream is shifting towards smaller displacement diesel engines,” said Suehiro Hasshi, the project leader for the Civic i-DTEC development.

“There will be a natural evolution of the 2.2 and some improvements but we will also produce other versions of the 1.6 with different power outputs.”

In the Civic, the new 1.6 – also destined for the Swindon-built CR-V SUV – provides a class-leading blend of performance and efficiency. It develops 118bhp and 300Nm of torque but is also potentially capable of 78.5mpg with CO2 emissions of 94g/km.

This is down to a combination of low weight and reduced friction, said Hasshi. The all-aluminium engine weighs 47kg less than the 2.2 and another 7kg has been saved with the introduction of a new six speed manual gearbox. Internal friction has been reduced 40% compared with the 2.2.

Hasshi said the new gearbox was essential to get the best from the new engine.

“With such a highly sophisticated engine there was no way we were not going to optimise the transmission,” he said. “The one for the 2.2 engine is not bad but it was originally designed for our high torque V6 petrol engines and was not really suitable for the 1.6.”

Honda’s small diesel is just the first of a new range of engines which will replace the entire current line-up over the next three years under the ‘Earth Dreams Technology’ tagline.

Honda insiders described it as their most important new engine in a decade and said it will soon be powering a quarter of all the cars the automaker sells in the UK.

It has currently been engineered to meet EU5 emissions standards rather than the tougher EU6 regulations due to come into force in September 2015 but Hasshi says this was because the new rules had not yet been fully defined.

“The content of the new legislation has not been fixed 100%,” he said, “so for a manufacturer to say it has an engine which is EU6-compliant does not make sense. The 1.6 can be made EU6-compliant but the legislation needs to be fixed first.”