Good grief man, he's not trying to cheat them. It's good PR for a company to give you a new engine when you wreck it. I know if i lost my air filter and wrecked my engine, i'd send it in to see if they'd replace it. If they gave me a new one or a rebuild, great, i'm happy with the company, and i'll tell my friends. If they didn't, oh well, i wrecked my engine and need to replace it myself.

It's bad advice to tell him not to send it in. You may have enough money to throw it around needlessly, but most of us can't afford to at least give a company a chance to make us smile.

Send it in with a letter saying the filter came off and now your engine is toast. You may get lucky.