My oil changes are when the DIC says to do so. It has been averaging between 8 - 10,000 miles. (When the DEF was going bad it would need to be changed every 3,000 miles). The stock fuel water separator filter also done with the DIC and it averages 40 - 50,000 miles. That was before the Lift pump installation and now it is at the 75,000 mile mark. The AirDog filters are changed every time that I notice the fuel mileage drop by 3 mpg's on an average run or when I hear that the pump motor starts to run noisier than normal. It seems to run good for about 30 - 40,000 miles. I change the spin-on transmission filter every 3rd oil change and the internal filter was changed at 279,000 miles when the dealership had to replace the factory wiring harness inside the transmission when it loosen up enough to leak fluid into the wiring harness and shorted out the TCM and 5th & 6th solenoids.