how you guys doing. well ive got a quick question. i just got my oil change at 21k at a mobil 1 lube shop. they said that i have to change my diffential oil cause there are metal shavings in the rear diffential. the liquid looked watery too. i took my car to the dealership at 15k for maintenance but they told me they dont do **** sometimes. so should i go and chagne it this week?