Here's some pictures of the Dodge with the Dual-Bypass filtration system; which is mounted on the passanger side frame rail you can see the filters "hanging down". Currently I have over 36,120 miles on the same oil, with oil analysis verification. Second is a PML 7 quart Aluminum Dana 70 rear differential cover with oil analysis port. With an extra 1 1/2 quarts of Amsoil severe gear 75w-140 gear oil I reduce the drag on the rear Dana 70 and get another 5% in fuel savings, also increasing the life of the rear differential . Amsoil severe gear oil is good for over 250,000 miles of sever towing/hauling or high hp/torque gasoline or diesel engines. Many on this site, time & time again have whinned about the price of petroleum products, and continually say diesels are not worth the extra cost? by reducing you oil change intervals you can reduce your fuel & overhead costs, and can weather these higher fuel prices. Simple switching your rear differential fluid to a synthetic gear oil can alone increase fuel economy up to 5%. Most truck owners surveyed neglected their rear differentials some never changing the rear differential gear oil, until some type of noise or vibration; at which point the damage is already done.