The pilot was cruising at 8,200 feet mean sea level (msl) in his experimental category airplane, when he heard a sudden change of sound from the engine and noticed his oil pressure drop to zero. He executed an emergency landing on a paved county road. The landing gear wheels of the airplane were located on the tips of the lower wings, 16.4 feet apart. During the landing roll the right wing tip landing gear hit soft dirt and gravel, and the airplane spun to the right. Upon examination of the airplane the pilot stated that his engine oil level was full and there was no indication of an oil leak. He suspected that the oil pump failed on the experimental category engine.