Swiss scientists say they've developed a hybrid natural gas/diesel engine that emits less than half the CO2 compared to a regular internal combustion engine.

Based on a system of sophisticated control engineering, the engine can also offer gas mileage of 117 miles per gallon, scientists at the Swiss Federal Institute of Technology reported.

As global energy markets are changing with increased discovery of natural gas deposits, natural gas could become an important fuel for vehicles on the world's roads, they said.

The researchers redesigned a conventional diesel engine of a VW Golf to run on 90 percent natural gas; instead of the spark plugs normally found on natural gas engines, combustion if accomplished by injecting a small amount of diesel fuel directly into each cylinder.

While natural gas-diesel engines already exist, usually as stationary engines to generate electrical power, creating one to power vehicle came with several challenges, they said.

"In a vehicle, the engine speed and load change constantly, which means the engine system is far more complicated," Tobias Ott, a doctoral student at the Swiss institute, said.

The scientists said they believed such a natural gas-diesel engine for vehicles could be in production in 5 years.

"The prerequisite is that we find an industrial partner who can take charge of developing a prototype," researcher Christopher Onder said, adding the group was already engaged in negotiations with an unnamed car manufacturer.