Against this backdrop, Firestone Tire and Rubber Company decided to sprinkle some radioactive magic into spark plugs. The theory behind radioactive spark plugs was quite simple from an engineering perspective. Thus, the polonium-210 spark plugs would theoretically create a better, stronger spark and improve combustion efficiency. The most conclusive test of this type consisted in comparing the starting characteristics of many polonium-containing spark plugs with ordinary spark plugs, all plugs having had more than a year of hard service, in several engines at -15° F. It was found that thirty per cent fewer revolutions of an engine were required for starting when the polonium plugs were used. If the radioactive spark plugs had serious performance benefits, one suspects they might have stuck around.