Toyota introduced a straight-six truck diesel engine in 1956, named the 1D, displacing and its next iteration, the 2D displacing . The H series of straight-six diesel engines were built for nearly 23 years. In 1990, the naturally aspirated engine 1HZ and the turbocharged 1HD-T engine were introduced. The 1HD-T engine was initially used in the Toyota Land Cruiser 80 series and culminated with the EFI equipped, 24 valve, single-camshaft 1HD-FTE, found among others in the Toyota Land Cruiser HDJ100. The 1HZ engine has a single overhead camshaft, 12 valves and produces from its capacity. The engine was offered for Land Cruisers in the 70, 80, and 100 series, as well as in Coaster buses. In production for more than 23 years with only minor modifications, the 1HZ is still used today in the 70 series and Coaster buses and sold mainly in Australia, Africa, and South America. The Yanmar 6LPA-STP marine engine is based on the Toyota 1HD-FT engine.