My Ford 170 cu. in. 6-cylinder engine lost all compression in one cylinder, so before rebuilding it I disconnected three spark plug wires (every other one in the firing order) to see how it would run on three. It ran, but not very smoothly. I just drove it up and down the driveway a couple of times. I've heard of people plugging the intakes on a few cylinders of an 8 to save gas during the war. World War II that is, the next one after the War to End All Wars.