Some of the most highly rated synthetic motor oils are Amsoil Synthetic 10W-30, Pennzoil Platinum Full Synthetic and Castrol Edge with Syntec Technology, according to BestCovery. There are various performance tests that measure motor oil quality, so the highest rated oil varies by test.
Amsoil Synthetic 10W-30 is the most expensive synthetic oil on the market as of 2015, but it performs best on the basis of oxidation stability, high temperature viscosity and four-ball wear scar tests, as reported by SmartSynthetics. Both Pennzoil and Castrol Edge synthetic motor oils are more widely available and less expensive than Amsoil, but require some compromise in the area of performance.
While synthetic motor oil costs more per quart than regular petroleum-based motor oil, it offers some advantages over conventional oil. These advantages include better engine protection, extended engine life and longer periods between oil changes, as stated by J.D. Power. Synthetic oils can tolerate high temperatures well without breaking down and creating the engine sludge left by conventional motor oils.
Standard vehicles do not require synthetic motor oil, as it is intended to protect engines operating in extreme conditions. Full synthetic oil was initially used as jet fuel during World War II, according to Edmunds.