Cutting an old oil filter open is a great way to learn more about what's going on inside your engine. The best and easiest way to do it is to hrab yourself a filter cutter. It's basically a bigger version of a tubing cutter. It centers in the threads of the filter and you tension the cutter wheel slightly and spin. Light tension is best and lots of spins, let the cutter do its work. Be careful once its cut, it leaves a sharp edgs. All oil filters are NOT created equally. A good filter will have