Not sure why anyone buys a new tensioner when all you have to do is remove the pulley wheel, open the rubber seal on the bearing and grease it with a needle. Pack the grease in with your fingers and put it back together.

I've never bought a new tensioner.or idler wheel. For that matter, one of my serpentine belts is almost 20 years and 300,000 plus miles old. Never had a problem.