Walmart offers the Mobil 1 Full Synthetic Motor Oil 5-Quart Jug in several varieties for $22.88. This $12 mail-in rebate cuts it to $10.88. Opt for in-store pickup to dodge the $5.99 shipping fee. That's tied with our mention from a week ago and about $18 less than you'd pay at local auto parts stores after the same rebate. Buy Now