Do the math. It's possible that this isn't the great deal it appears, even with the $10 coupon. I don't know the exact numbers, but I think these are pretty close for the stores around here. Let's say Mobil1 is $8.99 a quart at Autozone. Buy five quarts and use the coupon and it's $34.95 for those five quarts, or $7 a quart. I'm pretty sure you can still get a five-quart jug of Mobil1 at Walmart for somewhere around $24.97 ($5/quart), and a six-quart case of Mobil1 at Sam's Club or Costco for around $36 ($6/quart), either of which is a better deal than using this coupon on $8.99 quarts at Autozone.
Maybe my numbers are off, and maybe the prices at your local stores are different from mine, and this coupon at Autozone is a better deal than the other places. But don't assume it to be true without checking the numbers.