Castrol GTX Motor Oil, SAE 5W-30, 1 qt (946 ml) for $2.99

From Buxr.com on 05/24/12

Maximum protection against both viscosity and thermal breakdown. Superior sludge protection. American Petroleum Institute certified. For gasoline engines. Castrol GTX's superior sludge formula is so powerful, it passed one of the world's toughest sludge tests. It's more than just oil. It's liquid engineering. Stop-and-go traffic. Harsh weather conditions. Extending your drain. These severe driving conditions can all cause sludge to build up in your engine, leading to reduced gas mileage, decreased performance, and in some cases, engine seizure. Protect your care from harmful sludge formation with Castrol GTX. Unique dual-action dispersants provide superior protection against sludge build up (5W-30s tested vs. leading competitor)