Just throwing this out there.. but since you are looking for a 5w40 from walmart...
Delo XSP 5w40 - $19/gal.
Delo 400 XSP SAE 5W-40 with ISOSYN Advanced Technology is a mixed-fleet motor oil recommended for naturally aspirated and turbocharged four-stroke diesel engines and four-stroke gasoline engines in which the API CK-4, API SN or API SN PLUS service categories and SAE 5W-40 viscosity grade is recommended. It is formulated for engines operating under severe service and a wide range of climatic conditions.Delo 400 XSP SAE 5W-40 with ISOSYN Advanced Technology is excellent for use in engines developed to meet 2010 emissions standards and in engines equipped with features like four-valve heads, supercharging, turbocharging, direct injection, shorter piston crowns, higher power density, intercooling, full electronic management of fuel and emissions system