Royal Purple Synthetic Motor Oil is designed to protect your engine against wear by using specially formulated Royal Purple additive technology that not only protects but also reduces engine friction which improves horsepower, reduces emissions and increases fuel economy. Royal Purple oil is so advanced that it's designed with alternative fuels in mind such as ethanol and features extensive compatibility with such fuel to prevent white sludge and lubrication starvation even in situations where there is 20% ethanol use. Royal Purple synthetic oils have superior corrosion protection and in lab tests there was no rust found in industry corrosion tests. This oil features extended emissions protection that optimizes catalytic converter life due to the patented ZDDP additive found in the oil. Royal Purple Synethic oil is highly recommended for both stock or modified engines.