That's about right, but I started doing extended drains with oil analysis. I believe the oil that is in my truck right now has been in there for about 11,000 miles. I changed my oil filter when I took my oil sample at about 8,000 miles. I am using Mobil Delvac 1 5w-30 synthetic too.
25K intervals are for gas rigs. Diesel vehicles are set at 15k without ypass kits, and unlimited with oil anyalisis and bypass kits. Great stuff, Amsoil. I use it in everything, including my lawnmower. Thats one more quart of oil I didn't have to buy from the oil quintrillionares, I mean companies.:drink