The thing you should know about motor oil brands is that there’s very little difference between different brands of motor oil. What matters is the oil's viscosity grade (10W-30, for example) .  You must use only what the owner’s manual specifies. Whatever brand of motor oil you use, just make sure you change your oil regularly, following the recommendations in your vehicle owner’s manual. The manual will also tell you what kind of oil your vehicle needs, conventional or synthetic oil. Lastly, if your engine is leaky, parts are worn out, it won;t matter how great a motor oil / motor oil additive you have put in.

In the U.S., all motor oils in the market are tested by the American Petroleum Institute (API). If the oil meets certain minimum qualifications, the manufacturer can place the API star logo on the package. Look for the logo. There is also General Motors’ Dexos certification. An oil carrying the Dexos logo meets a more stringent set of requirements, but since GM charges brands much money for carrying the logo, not all motor oil brands carrying this additional certification.

Full synthetic motor oil are expensive. Some can cost as much as three times as much as conventional oils. 

Overall, Mobil 1 is the best motor oil.