What Propane Engines Say About Spark Plugs

Spark plug and ignition voltage requirements were determined for a typical medium duty truck engine in four configurations: production gasoline version; dual gasoline-LPG carburetion; full LP-gas conversion; full LP-gas conversion with compression ratio increased from 7.6 to 8.93:1.

This paper shows that spark plugs only one range colder should be used when converting from gasoline to LP-gas operation. Very cold running plugs are undesirable because of the higher sparking voltage requirements.

Cylinder-to-cylinder variations in spark plug temperature were also found to be much greater using LP-gas.