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Discussion Starter · #1 ·
I have read all kinds of posts on here and other forums on the great who's better oil debate. It got old really quick. This is my 1st new car so I wanted to switch to synthetic after break in. I narrowed it down to either Mobil1 or RP 5w30. I noticed RP is NOT on the list of GM approved oils (GM6094M) so I sent them an email asking why not and if it would void my warranty. Heres the reply:
The oil specified for your Camaro is a 5W-30 that has the API Starburst symbol on it. Also, the oil must meet the GM 6094M performance spec. All Royal Purple motor oils meet or exceed the performance requirements of GM4718M, and GM6094M. The GM 4718M spec is largely an oxidation testing sequence GM began using back in the mid to late 1990’s with the introduction of the C5 Corvette. The new design created some inherent issues with oil cooling. GM needed an oil which could handle higher temperatures for extended periods without a significant increase in the oxidation rate. In 360F Thin Film Oxidation Uptake (TFOUT ASTM D4742) testing, Royal Purple SAE engine oils exceed 1200 minutes before failure. Most synthetics, including GM4718M licensed Mobil 1, will typically reach failure in less than 500 minutes.

The GM 6094M specification is a low temperature cold cranking viscosity. The pumping viscosities specified by GM6094M are shown below. The Royal Purple pumping viscosities are shown for comparison. I have also attached the Royal Purple motor oil data sheet:


For 0W-XX oils - 30,000 [email protected] -40°C
For 5W-XX oils - 40,000 [email protected] -35°C
For 10W-XX oils - 50,000 [email protected] -30°C

Royal Purple:

For 0W-40 oils - 20,000 [email protected] -40°C
For 5W-20 oils - 22,200 [email protected] -35°C
For 5W-30 oils - 34,800 [email protected] -35°C
For 5W-40 oils – 21,500 [email protected] -35°C
For 10W-30 oils - 18,000 [email protected] -30°C

Higher numbers indicate a thicker, or more viscous fluid. As can easily be seen, Royal Purple motor oils have much better cold flow (lower pumping viscosities) than required.

Even though Royal Purple motor oils meet or exceed the performance requirements of GM 4718M and GM6094M, we cannot list certification because the GM specs also require an API SM rating. We also can not show the API Starburst logo because we do not carry the API SM rating. We have held most of our motor oils back from API SM (most RP SAE motor oils are API SL) because of the lower amount of anti-wear additive allowed in API SM/ILSAC GF-4 oils. The reason for the restriction on anti-wear additive is that certain components of anti-wear additive were shown to cause premature degradation of catalytic converters. OEMs are now mandated by the EPA to warranty the emission system separately from the power train. Rudimentary experimentation showed certain anti-wear additives do in fact degrade catalytic converters; however, the anti-wear additive was applied directly to the core of the cats during the tests. If enough oil is consumed in the combustion chamber (i.e. through poor piston ring seal and/or leaking valve seals), there can be degradation in catalytic converter life. This is not an issue with Royal Purple motor oils used in a mechanically sound engine. The OEMs are willing to trade the longevity of the engine for a possibility of extending the life of the catalytic converters.

We do not agree with reducing anti-wear protection for the engine. For our customers who have vehicles under an OEM warranty that require API-SM rated oils, and have chosen to use Royal Purple API-SL oil, we offer a corporate warranty in the case that engine damage or failure is directly attributable to Royal Purple Oil. I have attached a copy of the warranty for your review.

In summary, Royal Purple motor oils are not currently warranty compliant for your Malibu. If strict warranty compliance is your primary concern, we may not be the best choice. However, if performance and protection are your primary concern, Royal Purple SAE 5W-30 (part #01530, quart bottle) would be an excellent choice. We also offer a retail warranty for our customers under OEM warranty, that use our SL oil instead of the recommended SM oil. Please see attached.

Thanks for choosing Royal Purple and have a great day!

Best Regards,

Christopher Barker
Tech Services
Royal Purple, Inc.
1 Royal Purple Ln.
Porter, TX 77365

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So, the short version.

The manufacturer is more worried about the catalytic converter than the engine, and there is a possibility that the additives in Royal Purple might degrade your cat.

IMO it's a lot of technobabble. I have some friends who swear by Royal Purple, and I know others who won't touch the stuff with a 10' pole. I personally used Mobil 1 in the last performance vehicle I owned, b/c that was what was specified by the factory. I haven't seen any solid evidence that Royal Purple provides any extra performance or protection... it's all a personal choice.
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