Show I OWNERS REPLACE CAR SPARK PLUG Annual Practice Has las Advantages Advantages Ad Ad- vantages in Better Mot Motor r Work Vork and Economy May I 5 to 11 hns been ben designated us as Change Week for JU Itt 1020 9 O During that lint time limo millions of motor motorcar motorcar car owners will replace the spark plu plugs s In iii their cars with new sets havIn having hav tiny In ing learned 1 by experience that the practice bins lias advantages nd In economy conomy and ond Improved engine performance One reason renson wh why spark plugs should bo be clanged changed nt at least once onre n II year Is shown In the hue accompanying photomicrographs of or n a spark plugs plug's electrodes after that length of service Electrode Burned Away The center electrode Is burned own away The ground electrode Is ts likewise pitted pit ted and burned on and Its surface Is no longer parallel to that of the time center electrode This results In a small spark of no great greut Intensity and agap agap a n gap setting altogether too wide forthe for forthe forthe the spark slark to 10 jump under load conditions condi condl thong heavy pulls and rapid tion Obviously the corrosion means menns a weaker spark n a beav heavy loss o 0 power and waste of fuel Exhaustive laboratory tests have proved that each spark plug fires Ores Its k sM d These photomicrographs photomicrograph show chow what a spark plug plu looks like after firing an automobile engine twelve The crusted carbon surface of the Insulator and the pitted electrodes divert the current which Is II weakened weak ened and diffused Instead of sending sending send end ing a hot Intense spark cross ucross the gap pap with the result that fuel and power are wasted Engineers advise changing spark park plugs plug at least once a year In automobiles and oftener In power plants plant of tractors tractor trucks truck and stationary engines charge more mure than thun times In to driving a car miles mills The Intense nse heat bent the ravages ra of chemical reactions reaction which are ore set up till and th the tremendous mechanical shock to which spark Irk plu plugs are subjected In such lIuch an ordeal Inevitably take their toll toil incrusted With Carbon The Insulator becomes encrusted with bits of or carbon In time lime crud and with the aid uld of Intense temperatures these carbon particles panicles Impregnate the he surface of the Insulator causing a Q purl partial la I short circuit The r result sull In Inthe Inthe inthe the of at the spark plug Is ts n a dif dlf diffusion hit hit- fusion of current from fromn toe the electrode f a o consequent loss long 8 of at Intensity In the tI- spark and ond of ot e In engine vp- vp fIern p ern lion experiments of ot automotive magi enl veers have hll shown that changing spark pi plugs U S every ery miles or once u I year not nol only saves sates their cost In cosand ens cos II and oil hilt but restores In surge measure lIsure new car power speed and and o I lion with nil 1111 the pleasure that any car cor owner O derives from these features of 01 bl motoring |