Walmart offers the Mobil 1 10W-40 High Mileage Full Synthetic Motor Oil 5-Quart Jug for $25.47. Opt for in-store pickup to dodge the $5.99 shipping fee. That's the lowest price we could find by $11, although we saw it for $3 less in our mention from last August. It purports to reduce deposits and sludge, condition engine seals, and provide wear protection.
Reviewing this critical insurance policy takes a little effort, but it pays off big.