The Toyota 1HZ is a straight-six diesel engine developed and produced by Toyota Motor Corporation beginning in 1990. It continues to be offered in vehicles sold in countries with lax emissions regulations, and those sold by Toyota Gibraltar Stockholdings for organisations such as the United Nations.

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Toyota HZ engine
A Toyota 1HZ engine installed in the Land Cruiser.
Overview
Manufacturer	Toyota Motor Company
Production	1990–present
Layout
Configuration	Straight-6
Displacement	4.2 L (4,164 cc)
Cylinder bore	94 mm (3.70 in)
Piston stroke	100 mm (3.94 in)
Cylinder block material	Cast iron
Cylinder head material	Cast iron
Valvetrain	SOHC with 2 valves per cylinder
Valvetrain drive system	Timing belt
Compression ratio	22.4:1
RPM range
Max. engine speed	4000
Combustion
Fuel system	Mechanical fuel injection
Fuel type	Diesel
Oil system	Wet sump
Cooling system	Water-cooled
Output
Power output	131 PS (129 hp; 96 kW)
Torque output	285 N⋅m (29 kg⋅m; 210 lb⋅ft)
Chronology
Predecessor	Toyota H engine

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The 1HZ generates more power and torque than the previous 2H diesel engine. Despite being 30 years old, the 1HZ still sees use in Landcruiser 70 Series production worldwide with the exception of petrol-only markets and Euro 4 and Australian markets, where the 1GR-FE and 1VD-FTV Turbo-Diesel is supplied respectively. A popular engine in the 80 series Land Cruiser, it replaced the 2H engine in the 80/85 series by 1990.

The 1HZ Toyota Landcruiser 4.2 litre (4164 cc) diesel inline 6-cylinder 12-valve SOHC (single overhead camshaft) is of the IDI or indirect injection design, and delivers maximum power of 96 kW (129 hp) at 3800 rpm and maximum torque of 285 N⋅m (210 lbf⋅ft) at 2200 rpm.

The 5-cylinder variant of this engine is known as 1PZ.

Toyota KZ engine