The airplane contacted a guard rail and a ditch during a forced landing on an interstate highway following a total loss of engine power. The pilot reported he initially flew past his intended destination airport and was turning back to the airport when loss of power occurred. He stated they were at 3,000 feet mean sea level (msl) when the engine started to sputter intermittently. He reported that he immediately checked the engine gauges which looked normal, and he switched fuel tanks. The pilot reported that upon reaching an altitude of about 2,000 msl, the engine stopped producing power. The pilot reported he applied carburetor heat and since he had the mixture leaned, he moved the mixture control to full rich. The pilot stated he attempted to restart the engine to no avail. The pilot reported his choices of a place to land included a small field, a gravel pit, or the highway. He chose the highway. He reported that he intentionally kept his speed between 75 and 80 miles per hour during the landing to match the speed of the traffic on the highway. The pilot reported that during the landing the airplane bounced and contacted a guard rail. The airplane then spun around and contacted a ditch prior to coming to rest. Following the accident the airplane was secured on a flat bed trailer and an engine test run was conducted using an alternate fuel supply. According to the Federal Aviation Administration inspector who over saw the test, the engine started and ran smooth up to 1,900 rpm. No mechanical failure/malfunction was found which would have resulted in the loss of engine power.