Mercedes-Benz rewrites engine rules

Friday, August 10, 2007

DiesOtto combines best of petrol and diesel
Engine combines performance and economy
Expect to wait five years until you can drive one

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Mercedes-Benz is combining diesel and petrol technology to create a more environmentally friendly engine.

The 1.8-litre DiesOtto engine runs on standard petrol. However, it offers the pulling power and frugal fuel consumption of a diesel as well as the power and cleaner emissions of a petrol engine.

As in any petrol engine, the DiesOtto engine has spark plugs at the top of each cylinder, but they don't fire on every cycle.

They will fire if the driver accelerates hard, but otherwise the engine will rely on compression to ignite the fuel mixture, just like a diesel engine.

The result is that it is able to run more economically in more mundane motoring situations, but increase power - and fuel consumption - if a driver wants to accelerate hard.

It offers 238bhp and 296lb ft of pulling power, which is the equivalent of a standard 3.5-litre V6 petrol engine or a 3.0-litre V6 diesel.

The engine is not expected to appear in production cars for at least five years, but units have already been tested.

Cost is believed to be the main limiting factor at present.

The engine, which will be on show at the Frankfurt motor show in September, takes its name from the word 'diesel' (after Rudolf Diesel, its inventor) and Nikolaus Otto, the inventor of the petrol engine.

• We'll have all the latest news from the Frankfurt motor show - come back on September 11 to see all the new cars.