Spark plug question

[Scott from Marshfield]

Hey quick question will these spark plugs work for my 1965 farm all cub? I found a bag of 4 them in the barn- they say NGK AB-6

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[Eugene]

It cross references to a Champion D21. Should/will work.

[tst]

that # crosses to a champion D16, it will work but is a "colder" spark plug

[radioguy41]

"Colder", meaning if you're burning any oil the colder plug will foul sooner than a hotter plug, especially in cooler parts of the country where the engine is likely to run slightly cooler.