The Rover Company used straight-sixes in many of its saloon cars. A family of straight-4 and straight-6 engines with an unusual 'Inlet-Over-Exhaust' layout were developed. Introduced in the 1930s, these engines were used with great success in Rover's post war cars (the 'P3', 'P4' and 'P5' models). The sixes were available in a variety of capacities- , , , and . In 1968, Rover began offering the engine as an option in long-wheelbase variants of its Land Rover 4x4. The engine remained available in the Land Rover until 1980, long after production of the other versions of the Rover IOE straight-six had stopped.