Radial engine

If oil ran out, that engine needed to be shut down.

Finally, Radial shared another problem with the inverted Vs.

While the engine was static, meaning not running, oil gradually seeped past the piston rings into the combustion chambers of the inverted, meaning the bottom, cylinders.

If too much oil pooled in a lower cylinder head, the piston cannot reach the end of its stroke because liquid cannot be compressed, and it cannot escape through the valves fast enough.