I don't know what is best. But the guys that I know are in the 4k-5k range. I guess they tow alot. Maybe your master mechanic doesn't. That would work out. Chris drives an Excursion with a 7.3 Powerstroke like some people drive a Kia. I'll bet he changes sooner than 7500. But I have no dog in the fight, and everybody does their own thing. I think that being a boater and building new power before has made me a conservative oil changer. When I change my oil in my Malibu at 3k, the oil life light (from GM) thinks that it has 2000 miles left, but that's ok. I'll err on the side of caution. Plus, I keep my vehicles a long time and this plan (early rather than late) has worked great for me. :cheers2: