I always use Moroso. I buy a case from a local dealer. If you buy them from singles, their very expensive, around $10. Wix are good quality also & are cheap. We use them on our sprint car & have never had a problem. (but, we change the
oil after every race) I also cut open the filter on both cars to see if there's any metal or debris. It's a good practice, can save a expensive motor !