On May 5, 2015, about 1024 eastern daylight time, an experimental, amateur built Fischer RV-7, N364SJ, was substantially damaged during an emergency landing near Bartow, Georgia. The commercial pilot received minor injuries. Visual meteorological conditions prevailed, and no flight plan was filed for the personal cross country flight, which departed from East Georgia Regional Airport (SBO), Swainsboro, Georgia about 1000 and was destined for Gwinnett County Airport-Briscoe Field (LZU), Lawrenceville, Georgia. The personal flight was conducted under the provisions of Title 14 Code of Federal Regulations Part 91. The accident flight was the beginning of a planned cross-country flight to Wyoming. On the morning of the accident, he noted that the oil level was 1.5 quarts above the minimum. The pilot conducted an engine run-up check prior to takeoff and observed no anomalies. After departing SBO, the pilot initiated a climb and established a direct course to LZU. About 5 minutes after takeoff, the pilot leveled the airplane at 2,500 feet mean sea level and configured the airplane for cruise flight, but the engine would not exceed 2,100 rpm; 300 rpm below desired cruise power. He attempted to manipulate the mixture and activated the electric fuel pump, but the engine power remained steady at about 2,100 rpm. The pilot elected to make a precautionary landing at a nearby airport, but moments after he diverted, the engine oil temperature increased "quickly" and oil began to cover the windshield. The pilot subsequently attempted a precautionary landing on a dirt road, but the left wingtip impacted the ground, the airplane cartwheeled, and came to rest inverted, resulting in substantial damage to the wings and rudder. The 1015 recorded weather observation at Kaolin Field (OKZ), Sandersville, Georgia, located about 13 nautical miles northwest of the accident site, included winds from 060 degrees at 5 knots, clear skies, 10 miles visibility, temperature 22 degrees C, dewpoint 15 degrees C, and an altimeter setting of 30.33 inches of mercury. The pilot held a commercial pilot certificate with ratings for airplane single-engine land, instrument airplane, and instrument helicopter. He reported 3,000 hours of flight experience, of which 300 were in the accident airplane make and model. His most recent FAA second class medical certificate was issued May 4, 2014. The airplane was a single-engine, low-wing, fixed tricycle-gear airplane. It was powered by an experimental engine rated at 180 horsepower that resembled a Lycoming O-360A1A reciprocating engine. A review of aircraft maintenance records revealed that the airplane had accumulated about 38.1 hours since its most recent condition inspection, which was completed on April 20, 2015. At the time of the inspection, the airframe and engine had accumulated about 364.4 total hours of operation. Postaccident examination of the airplane by a Federal Aviation Administration inspector, with assistance from an airframe and powerplant mechanic, revealed that the forward crankcase seal on the engine was intact, but had separated forward of the crankcase. Approximately 10 gallons of non-ethanol 90 octane automotive gasoline was drained from the wing tanks at the accident site. The spark plugs were removed and examined. All plugs, with the exception of the number 1 top plug, were secured properly and appeared normal in wear. The number 1 spark top spark plug was removed by hand and exhibited normal operating signatures. The magnetos were not examined, and magneto timing could not be verified due to impact damage. Further disassembly of the engine revealed that portions of the number 1 cylinder wall, compression rings and oil control ring had been burned through, and the number 1 piston head also exhibited thermal deterioration and pitting on the piston face. The numbers 2, 3, and 4 cylinder combustion chambers and their associated pistons displayed normal operating signatures. According to the last engine logbook entry, the engine was inspected in accordance with the condition inspection checklist provided by the manufacturer. According to Sky Ranch Engineering Manual, detonation is a process of self-ignition or explosive combustion that occurs when the unburned charge of compressed fuel reaches a critical temperature in the cylinder. According to a service letter issued by the engine manufacturer, "Use of lower-than-specified octane fuel could cause detonation and mechanical damage to the engine." The service letter did not list 90 octane rated fuel as an approved automotive fuel for use in this engine.