How many of us have learned this the hard way though? It's always the cheap stuff that bites you. A five dollar tube of grease versus three hours of your life you'll never get back, plus the customer standing there watching you get soaked. Same deal with those little rubber boots on coil packs. People skip them because they look fine, then water gets in and now you're chasing a misfire in a parking lot at midnight. The parts are never the expensive part. It's the callback that kills you.