I believe the greatest invention that does not use electricity in the Car engine specifically the diesel version.

The Gasoline version uses electrical sparks, however the diesel engine combusts heat and pressure to start and run.

The diesel engine does not need volts and if volts are not required than electricity is not involved.

Diesel vehicles when introduced did not only change the place where it was introduced, but changed the transportation medium of the whole world and hence it should be considered as the greatest invention that does not use electricity.