For its Prime members only, Amazon offers the Quaker State Advanced Durability 5W-30 5-Quart Motor Oil, model no. 550038280, for $13.97. Checkout via Subscribe & Save to cut that to $11.87. With free shipping, that's about $2 under the price you'd expect to pay at your local store.
Be sure to cancel Subscribe & Save after your order ships to avoid being billed for subsequent shipments.