Primarily, this depends on what you use your vehicle for. Consider these four basic types of uses:
Standard: If you use your car for normal, everyday driving, we recommend our signature high performance synthetic oil: Royal Purple API-licensed Motor Oil, which holds current American Petroleum Institute (API) and International Lubricants Standardization and Approval Committee (ILSAC) licenses, and is available in several viscosities. This lubricant is warranty compliant for newer vehicles, and offers the best protection possible in an API-licensed motor oil.
High Mileage: If your car has 75,000 miles or more, you should choose a premium full synthetic motor oil specially formulated for older vehicles. Over time, seals can shrink and leak; Royal Purple HMX™ High Mileage motor oil reconditions seals, providing a little swell and flexibility to older seals. HMX oils also provide a higher level of anti-wear additive than Royal Purple API-licensed oils and include a healthy dose of Royal Purple’s proprietary Synerlec® additive technology, further enhancing performance and protection.
Higher Performance: For car enthusiasts with high-end and modified engines, or motorists looking for an even higher level of performance and protection, Royal Purple HPS™ (High Performance Street) takes lubrication to the next level. Ideal for gasoline and diesel engines alike (except HPS 5W-20), Royal Purple HPS oils are unlicensed performance upgrade street oils and may not be strictly OEM warranty compliant for newer vehicles.
Highest Performance: The preferred choice for dedicated competition engines, and those that want their car to use the absolute best engine oil, Royal Purple XPR (Extreme Performance Racing) motor oils offer the ultimate in lubricant performance and protection. These oils are not a typical choice for daily driver and other street cars because of the much higher price tag. However, XPR engine oils offer enough protection for the most powerful race engines and, unlike most “race” oils, are completely safe for extended use in street cars.