How do you make a diesel engine more efficient? One answer may surprise you: Run it on gasoline.

That's what researchers at Sweden's Lund University are doing, and they believe this combination could cut both fuel use and emissions in heavy-duty trucks.

Lund's experimental engine uses a different combustion process, called Partially Premixed Combustion (PPC), which researchers say could increase a large truck's fuel efficiency by 50 percent.

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This process uses two fuel injections for each combustion, the ratio of which can be changed to alter the behavior of the combustion.

This in turn allows for control of ignition delay--the time between fuel injection and combustion--which ensures that fuel is burned more efficiently.

Tough Tractor Trailer

Tough Tractor Trailer

According to Bengt Johnasson, a Lund professor specializing in combustion engines, the process significantly reduces particulate and NOx emissions, to the point that a production engine might not even require a catalytic converter.

The current test engine operates at 50 percent efficiency, compared to around 40 percent for standard diesel engines.

With further testing, Johansson hopes to achieve levels as high as 60 percent efficiency.

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A more-efficient engine for large trucks could have a big impact on the overall emissions of the U.S. vehicle fleet.

Trucks rack up far more miles than passenger cars--with far worse fuel economy--so they produce a disproportionate amount of emissions.

Last week, President Barack Obama instructed the Environmental Protection Agency (EPA) to develop new fuel-efficiency rules for medium and heavy-duty trucks.

The new rules will follow fuel-economy standards passed in 2011, which call for a 10- to 20-percent increase in efficiency by 2018, depending on the class of vehicle.

Picking up where those rules leave off, the new standards will run from 2019 through 2025, to bring big trucks into line with the Corporate Average Fuel Economy (CAFE) standards for passenger vehicles, which run through 2025 as well.


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