The wide availability of the engine in the surplus market made it common until the 1930s, although it was considered unreliable for most of its service life.

[2] Curtiss continued the development of their V8 engines with demand for higher power outputs being largely driven by the US Navy’s requirement for seaplanes.

[3] Like most engines of the era, the OX-5's high-temperature areas were built mostly of cast iron, using individual cylinders bolted to a single aluminum crankcase, wrapped in a cooling jacket made of a nickel-copper alloy.

[4] The aluminum camshaft bearings were a split type bolted together and held in place by lock screws.

Certainly the JN4 with the OX-5 was underpowered, but the OX-5 proved a much better engine than the Hall Scott A7A that was the Achilles heel of the Standard J-1, the substitute primary trainer.

In particular the valve gear was fragile, and it had no provisions for lubrication other than grease and oil applied by hand, leading to an overhaul interval as short as fifty hours.

Also, the replacement of the A7A in Standard J-1s was contemplated, but the cost of $2,000 per aircraft compared with the need (by the time the J-1s were grounded in June 1918 JN-4s were in sufficient supply) led to the rejection of this idea.

The OX-5 itself would be replaced by the well-proven Wright Aeronautical-built version of the 150 hp Hispano-Suiza HS-8a V8 engine in the nearly 930 examples of the later production Curtiss JN-4H Jenny biplanes.