What’s in a name?

A lot when it comes to brand recognition. For example, you’ve probably heard of Royal Purple. The company has been making high performance lubricants for decades. Its products are used by competitors in NHRA, Sprint Car, Circle Track Late Model, kart racing, and other circuits. And Royal Purple motor oil is trusted by some of the top racers and engine builders in the industry.

While Royal Purple is clearly one of the more trusted names for motor oil and lubricants, things get a little murkier when it comes to the names of its motor oil. The company’s motor oil product line includes API, HPS, XPR, HMX, and HPM oil—plus other oils for motorcycles and dirt bikes. The names get an “A” for conciseness, but their meanings are about as clear as the oil itself. To clear up the confusion, we’ve put together this quick guide to choosing Royal Purple motor oil.

rpo-01520_rz_xlAPI-Certified Motor Oil

Breaking the Code: API = API-certified

Application: Warranted vehicles.

Overview: That API certification means this particular oil is certified to meet the automotive manufacturer’s standards, so you can use it without affecting the vehicle’s warranty. It’s a synthetic oil that has a combination of additives that provide good wear protection and optimize the life of the vehicle’s emissions catalyst system.

Available Viscosities (see our original post on deciphering viscosity): 0W-20, 0W-40, 5W-20, 5W-30, 5S-40, 10W-30, 10W-40, 15W-40, 20W-50.

rpo-31530_xlHPS Motor Oil

Breaking the Code: High Performance Street

Applications: High performance and modified engines.

Overview: Specially formulated for street performance vehicles that require a higher level of protection than the base API-certified oil, this oil is recommended for cars and trucks that are no longer under warranty. The synthetic oil features Royal Purple’s proprietary Synerlec additive, which improves the surface condition of metallic components and areas within the engine. This allows the oil to reduce friction even in modified, powerful engines. HPS oil also offers added viscosity to improve the sealing between the piston rings and cylinder walls and is fortified with zinc/phosphorous to reduce overall engine wear and work well with higher lift camshafts.

Available Viscosities: 5W-20, 5W-30, 10W-30, 10W-40, 20W-50


rpo-01041_si_xlXPR Motor Oil

Breaking the Code: eXtreme Performance Racing

Application: Multi-platform racing environments—NASCAR, NHRA, World of Outlawas, and Bonneville.

Overview: XPR motor oil is formulated to handle the heat, wear, and tear experienced in extreme racing engines. It features the proprietary Synerlec additive mentioned above for metal protection, but adds in other performance-enhancing additives. It comes in a variety of weights for specific motorsports applications and racing fuels.

Available Viscosities:
0W-5—ultra low viscosity for the most competitive classes such as Pro Stock, Comp Eliminator, and NASCAR Cup.

0W-10—for gasoline engines used in drag racing.

5W-20—works with alcohol, methanol, and nitrous oxide.

5W-30—designed for bracket racing, oval track racing, and other applications.

10W-40—made for marine, oval track, and endurance car racing where long periods of extreme heat are present.

20W-50—designed to handle extended periods of extreme pressure and heat and is ideal for sprint cars, tractor pulling, and bracket racing.

rpo-11748_bo_xlHMX Motor Oil

Breaking the Code: High Mileage (we’re not sure what the X stands for)

Application: Vehicles with more than 75,000 miles.

Overview: Another of Royal Purple’s synthetic oils with Synerlec additive, HMX motor oil is specially formulated to revitalize hardened seals, reducing oil consumption in the process. It also uses a combination of detergents to remove deposits and protect against corrosion. A zinc/phosphorous additive makes it ideal for use on flat-tappet engines.

Viscosities Available: 5W-30 and 10W-30

rpo-11629_xlHPM Motor Oil

Breaking the Code: High Performance Marine

Application: Marine engines.

Overview: Formulated for marine environments, this synthetic oil is certified NMMA FC-W Catalyst Compatible—the standard for marine engines with catalyst. A combination of Royal Purple’s Synerlec additive and high film strength delivers cooler operating temperatures.

Available Viscosities:  10W-30 and 10W-40

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Author: David Fuller

David Fuller is OnAllCylinders' managing editor. During his 20-year career in the auto industry, he has covered a variety of races, shows, and industry events and has authored articles for multiple magazines. He has also partnered with mainstream and trade publications on a wide range of editorial projects. In 2012, he helped establish OnAllCylinders, where he enjoys covering all facets of hot rodding and racing.