When you get new gears at Arizona Differential at 3601 n 36th ave Phoenix Arizona 85019, you get a complimentary 1500 Mile Oil Inspection. During this inspection we check the oil for any signs of excessive wear, grinding, or any other signs of failure. Our suppliers require this service in order to redeem your 12 month/12,000 mile warranty, if a problem should ever arise. We want to catch any problems as early as possible and keep you on the road or track for the long term!