About Royal Purple
Royal Purple was founded in 1986 by John Williams, a synthetic-oil developer whose formulators built the brand around a proprietary additive package called Synerlec -- a man-made compound designed to form high-strength ionic bonds with metal surfaces, boosting film strength and lubricity under sustained heat and pressure. The company built a 125,000-square-foot production facility in Porter, Texas, completed in 2004, and was acquired in 2012 by Calumet Specialty Products Partners, a refiner and processor of specialty hydrocarbon products headquartered in Indianapolis, Indiana, where Royal Purple now operates as a branded product line.
The lineup spans full synthetic motor oils, automatic and manual transmission fluids, gear oils, diesel and heavy-duty oils, and racing and specialty lubricants for automotive, commercial, and industrial use. On RevRated, Royal Purple is independently featured across three separate roundups: the HMX High Mileage Synthetic Motor Oil in our high-mileage motor oil coverage, the Max ATF High Performance Synthetic in our transmission fluid coverage, and the Synchromax Synthetic Manual Transmission Fluid in our manual transmission fluid coverage.
Brand website: royalpurple.com
What Royal Purple makes
Royal Purple's range runs wider than the products we review. The lines we know best from our own testing are marked with a star:
Full synthetic motor oils
conventional and high-mileage synthetic engine oils built around Synerlec additive technology -- featured on RevRated — featured on RevRated
Max ATF automatic transmission fluid
multi-spec licensed high-performance ATF for towing and modified vehicles -- featured on RevRated — featured on RevRated
Synchromax manual transmission fluid
synthetic synchromesh fluid for notchy manual gearboxes -- featured on RevRated — featured on RevRated
Gear oils
synthetic gear oils for differentials and manual gearboxes across GL-4/GL-5 specifications
Duralec diesel and heavy-duty oils
commercial and fleet-grade diesel engine oils
Racing and specialty lubricants
high-performance oils and additives for racing and industrial applications
Why we recognized Royal Purple
The RevRated Top Brand recognition isn't paid for and can't be applied for. We award it to the brands whose products consistently stand out in our hands-on category reviews. Royal Purple earned it on the strength of the products below, evaluated the same way every product on this site is: bought, run on real vehicles, and judged on merit.
Royal Purple products we rated highly
Royal Purple HMX High Mileage Synthetic Motor Oil 5W-30, 5 Quart
HMX runs the highest ZDDP anti-wear concentration in our high-mileage motor oil testing, formulated to compensate for wear on cam lobes and rocker-arm contact points after 100,000 miles. The seal-swell additive package is tuned above the industry norm, which is the right call for an engine already showing more than minor weeping at the valve cover, oil pan, or rear main, and the 15,000-mile drain interval splits the difference between standard high-mileage oils and the longest extended-drain formulas we tested. It carries a 4.9-star rating across 2,888 reviews.
Read the 8 Best Motor Oil for High Mileage of 2026 guide →
Royal Purple 01320 Max ATF High Performance Synthetic 1 Quart
Max ATF posted the highest film strength of any fluid in our transmission fluid roundup, built to hold an oil film on clutch and gear surfaces under loads that thin a standard ATF, which showed up in our testing as reduced operating temperature under sustained towing load. Multi-spec licensing across Dexron III/VI, Mercon V, ATF+4, and Type F gives it the same broad vehicle compatibility as a universal fluid while running the higher-performance additive chemistry. It holds a 4.8-star rating across 758 reviews.
Read the 7 Best Transmission Fluid of 2026 guide →
Royal Purple Synchromax Synthetic Manual Transmission Fluid - 1 Quart
Synchromax is sold and shipped directly by Amazon, removing the buy-box ambiguity that complicates some specialty fluid listings, and it backs that up with 1,895 reviews at a 4.8-star average, the second-deepest review record in our manual transmission fluid roundup. Owners repeatedly report it quiets notchy shifters in Miata and BMW E36/E46 gearboxes, and its light synchromesh viscosity (rather than a 75W-90 gear oil) matches what a lot of GM, Chrysler, and older import boxes actually call for.
Read the 10 Best Manual Transmission Fluids of 2026 guide →What earned Royal Purple the recognition
- Featured across three separate RevRated roundups: high-mileage motor oil, transmission fluid, and manual transmission fluid.
- HMX runs the highest ZDDP anti-wear concentration in our high-mileage motor oil testing, aimed at flat-tappet cam engines and existing seal wear.
- Max ATF posted the highest film strength of any fluid in our transmission fluid testing, with multi-spec licensing across Dexron III/VI, Mercon V, ATF+4, and Type F.
- Synchromax backs a substantial review record of 1,895 ratings at 4.8 stars as a widely-stocked option for notchy manual gearboxes.
- Built since 1986 on proprietary Synerlec additive technology, still central to the formulation of every Royal Purple lubricant today.