I think that many racers seem to like Royal Purple for racing. I wouldn't necessarily take that as a reason to use the same products on the street.

Their XPR oil products are for specific racing engines and fuels.

Their HPS products do not meet API certifications, and they are quite open about it. Kudos to them. They say why they can't pass those tests; it is because they made a conscious decision to add more of certain additives (like zinc) than engine manufacturers permit.

Their API-certified products are likely as good as any other current API product. I would just ensure that there is an API SM label on the bottle you purchase, since they sell so many different oils. But that is just me.

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2007 X3 3.0si, 6 MT, Premium, White

Retired:
2008 535i, 6 MT, M Sport, Premium, Space Grey
2003 X5 3.0 Steptronic, Premium, Titanium Silver
2002 325xi 5 MT, Steel Grey
2004 Z4 3.0 Premium, Sport, SMG, Maldives Blue