[rotorwrench]

We use two different types of spark plugs currently in aviation engines. Some folks want the massive electrode types since they are about half the price of the $110 each fine wire irridium electrode plugs. With massive electrode types, they will last about 200-hours if your lucky. The iridium tip fine wire type can last up to 800 hours so they are worth the price.

All of the folks that sell spark plug cleaning equipment are glad to sell you their abrasive. They use gray to black aluminum oxide for the most part. The glass beads will erode the sealant between the insulator and both the center electrode and the outer casing so it isn't recommended. The glass sort of jams in the crannies inside there. I know folks that have used glass bead and never had a problem but these engines have huge pistons so it likely doesn't matter all that much as long as the plugs are blown out well before reinstallation.

On car plugs, you just run them till they start missing and then throw them away & put in new ones. I don't know too many folks that take them out and clean them unless they are original type spark plugs. Now those can be cleaned.