The pilot reported that he departed with 60 gallons of fuel and, about 5 hours into an aerial observation flight, the airplane was not responding to throttle inputs and he decided to head towards a nearby airport to land. He descended to 2,000 ft, the airplane experienced a total power loss, and he realized he was not going to be able to glide to the destination airport. He turned towards a field and about 50 ft above ground, the airplane started gaining power and climbed to 100 ft. The engine experienced another power loss and he turned 180° towards the interstate and the engine surged a second time before losing power again. During the forced landing on the interstate, the airplane struck a car and came to rest in the grass adjacent to the road. Video provided by the Federal Aviation Administration showed no fuel drained from the left fuel tank and less than one-half cup of fuel drained form the right fuel tank. The airplane sustained substantial damage to the left horizontal stabilizer.