^^^i dont do that. i just get a really old rag, and put some vegetable oil in it. rub oil into the rubber, and it looks like new, until you wash it out when you wash your car. holds up well in the rain too. the rag is going to turn nasty black though. its a pita if your doing the rubber around the windows, so tape off the area with painters tape and newspaper, unless you want to have the fun of trying to get vegetable oil off the window without soap. only on the exterior though. works awesome on the wheel wells though.