[frnkeore]

When I was a mechanic, in the '60's, the shop bought their plugs 10 to a box. We'd take out 4, for a six and 2, ford a 8 cylinder.

It never made since to me, either but, that's the way it was. I just figured it was for bulk buyers that would by in multiples, like 60 for 6's and 80 for 8's. That's the only thing that made since to me.