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Show $ ! -I ! t- Why Spark Plugs J Must Be Changed Old or worn out spark plugs cause poor starting and exces- sive drain on the battery, poor ! running, fuel waste, and loss of I power, especially on hills. Often 4. large engine repair expense is .;. saved by simply installing a new ; 4 set of spark plugs, which is rec- .. ommended every 10,000 miles. 'X ; Tests show that n motor in which spark plugs had been used J for a little more than 11,000 miles developed 31.2 horse power, when run nt an engine speed ; J equivalent to 20 miles an hour. ! The same motor run nt the same speed equipped with a new. set of plugs gave a horse power 4 reading of 8S.0, an increase of 0.8 horse power. . . 't - J S I 'h- |