GM's diesel performance from a petrol

• Technology improves efficiency by 15%
• Engine damage is also reduced
• No on-sale date for system yet

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GM claims that its next generation of petrol engines will offer diesel-like economy and carbon dioxide emissions.

A new system, called Homogenous Charge Compression Ignition (HCCI), improves efficiency by burning fuel at lower temperatures and reducing the heat lost during the combustion process.

Worldwide tests with an HCCI-powered Vauxhall Vectra and Saturn Aura suggest they are 15% more fuel-efficient than a comparable fuel-injected engine.

There is also less engine damage, as fewer harmful nitrous oxide gases are produced, reducing the need for expensive treatments.

The system can be fitted to a conventional petrol engine, with only the exhaust system needing any modification.

A modified engine can still be powered by conventional forecourt petrol and bioethanol E85 fuels.

No date has been set for when the system will be on sale.