I understand the Do's and dont's that you listed(thanks) but I was just wondering if anyone had an approximate mileage mark that I could tell him. Like eg; in 1,000 miles you'll have to change or plan on changing at 500 miles. People always say carry an extra filter just in case, I for one cant afford to do that because if I'm on my way out to dinner or work or something like that I can't be crawling under my truck and changing filters. Thats why I was wondering if there was a ball park mileage that you can head off the unexpected.