Used a ton of Autolite 25 and 26 - My father literally bought 100 sets in a mixed lot of 25 and 26s at an auction (that's 800 plugs!!) for a dime a piece! eighty bucks and they were all new in the box - part of a bankruptcy sale - also bought a couple cases of Fram PH30 filters for .25 apiece and about a dozen cases of Havoline 10-30 for a dime a quart (remember the cans that you pushed a sharp spout in?). It was fun! We used them for a looooonggggggg time! No problems ever with the plugs (nor the oil or the filters). Did a lot of five dollar oil changes for friends and family!!