Well, after reading all the great advice all over this board I decided the best way to get my Durango to 500,000 was to totally make it synthetic. This weekend I added: Transmission: Amsoil Synthetic Universal Differentials: Amsoil 75w-90 Synthetic Gear Lube Transfer Case: Amsoil Synthetic Universal Power Steering: Amsoil Synthetic Universal Engine Oil : Mobil 1 Synthetic 10w-30 (To be changed when the dual bypass is installed in a couple of weeks). The vehicle has the 4.7 liter motor and 12,000 miles. i am done buying new vehicles for awhile because I am sick of car notes. I am going to attempt to get 500,000 miles out of it. Any suggetions or ideas anyone has are welcome of course. I will keep posting to let you know of my progress as I continue on this journey. I will be doing extended drains of course and look to the knowledgable ones here as to when would be a good time to schedule optimal fluid changes. I don't think that 25,000 mile changes are realistic. It is my daily driver and I don't drive that hard. 95% highway mileage to and from work.