Walmart offers the Mobil 1 10W-40 High Mileage Full Synthetic Motor Oil 5-Quart Jug for $22.88. Opt for in-store pickup to dodge the $5.99 shipping fee. That's $3 under our mention from three weeks ago and the lowest price we've seen. (It's the best price today by $10.) It reduces deposits and sludge, conditions engine seals, and provides wear protection.