No, won't harm the engine. If the old ones were bad then it might cause slight idle issues and poor fuel mileage but since you say the old plugs were not bad looking then you will be fine.
Of course it would be better to go ahead and just put a few more drops of sweat into it and get to those other 2 plugs ;)
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Thursday, July 30th, 2009 AT 11:17 PM