1. There is a sticker on fill tank. Refill with diluted Shell Rotella ELC add no SCA. I am using Rotella ELC diluted with 50 percent distilled water.<br/><br/>2. I have no idea the antifreeze age but the coach has 46000 miles.<br/><br/>3. No Coolant filter on the coach. My Cummins has no coolent filter specified in any of the manuals.<br/><br/>Do I need SCA additives if so what to get and how to...