Mercedes-Benz is developing the “DiesOtto,” a four-cylinder engine that combines features of both petrol and diesel motors to increase fuel efficiency, according to Reuters. The new engine will generate 238 horsepower and average about 40 mpg. The engine will use a spark plug to ignite the fuel/air mixture when starting and at high speeds, but at lower speeds, the engine will act like that of a diesel, without spark plugs. The engine will have a displacement of 1.8 liter and use gas direct injection to increase efficiency.