Teasel, R., Calcamuggio, G., and Miller, R., "Ignition Systems Can Affect Fuel Economy," SAE Technical Paper 650864, 1965, doi:10.4271/650864.
Some of the ignition systems currently being developed for gasoline engines have widely different electrical discharge characteristics. By selecting certain of these systems and by modifying conventional systems, the authors undertook an evaluation of the effect of the electrical discharge characteristics of the ignition system on fuel economy in current passenger car engines.It was found that changes in the electrical discharge characteristics from the present conventional ignition system could not improve fuel economy. However, a change in spark plug gap projection was found to be beneficial in the several makes of engines tested.Spark plug temperature recordings of typical vehicles in actual service indicated substantial low power operation. Tests based on low power accelerations revealed considerable losses in fuel economy and performance due to malfunctioning of the spark plugs which was undetected by the driver.