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.
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