in 1970. The 4.0 is one of AMC's best-known engines. It was one of four AMC engines kept in production when Chrysler bought AMC in 1987. Chrysler engineers continued to refine the engine to reduce noise, vibration, and harshness. The last in the line of the AMC inline sixes, the 4.0 is regarded as one of the best Chrysler 4x4 off-road engines. A Motor Trend long-term test of a 1997 Cherokee XJ noted "this long-lived OHV powerplant has a reputation for getting people where they need to go" as well as "much love expressed by owners for the torquey 4.0-liter/190-horsepower inline six." The engine is known for longevity, and can sometimes go more than without rebuilding. Also, the vibration dampener (harmonic balancer) usually gives out after 300,000 miles where it is common for the rubber insulation to deteriorate where a service replacement is warranted. Described "as reliable as a block of wood" by Popular Mechanics and ranked first among "the ten best car engines they stopped making in the past 20 years," the 4.0 L should run 200,000 miles before a rebuild is even expected and it is also able to "suffer running conditions that'd kill most motors." When introduced, the block-mounted oil filter check valve was eliminated on the 4.0 (along with the 2.5 and 4.2s manufactured after September 1986) when AMC engineers standardized their oil filters. The pre-1987 engines had an oil filter adapter with 3/4 (cylinder block end) and 13/16 threads (which used a GM oil filter common to Buick, Oldsmobile, Pontiac, and Cadillac V8 engines) while the 1987-06 engines were originally fitted with a metric thread filter (later revised in 1991 for the common 3/4 threaded Mopar and Ford V8 oil filter; the oil filter adapter was redesigned where the oil filter is positioned 90 degrees offset adjacent to the starter motor - a Ford V8 oil filter can be used in place of the short filter increasing oiling capacity). The first 4.0L engines in 1987 had a Renix (Renault/Bendix) engine management system considered quite advanced for their time. A knock sensor allowed the ECU to control spark advance in response to fuel octane and engine load. Unfortunately, there are few scan tools capable of interfacing with the system to pull diagnostics codes. RENIX systems also have no permanent memory for diagnostics codes thus making the diagnosis of intermittent problems more difficult. The 1987 RENIX 4.0