We have several large scale full building generators. Our exercise cycles are 15 minutes once a week. Our diesel mechanics fully service the engines every 3 to 6 months depending on size and importance.

Fuel is easy because we have an external tank with a visual gauge that you can read from several feet away. When they added DEF they neglected to add a DEF gauge that's as easy to read. Thank goodness they sell DEF at any old truck stop.