Why at time of delivery? Are you worried it wasn't filled correctly from the dealer or is it something else? If you are worried about it not being done correctly, do you change all your fluids when you get home or just that one?First at time of delivery or when I get it home, I doilt then too. Then after 30,000 or so give or take. There is nothing to ruin the oil in teh rear end,no blow by etc so it doesnt wear out like engine oil does. The tiny bit of hydrocarbens that get by the rings is what wears engine oil out.