Braden

Here is some information I have gathered in regards to the use of synthetic oil damaging operation of Rotary Engine.
Firstly I've messaged two major oil manufacturers.
Here is the response from Royal Purple, and on their website.
Royal Purple has performed seal compatibility testing on the components used in Mazda rotary engines with excellent results — including older rotary engine seals dating back to the Cosmo (mid to late 1960′s). Royal Purple’s former Technical Services Manager had owned and raced rotary engine cars using synthetic motor oils since 1985 with excellent results. Extensive research by the Royal Purple Technical Services department has been unable to determine a credible and valid technical explanation for this recommendation against the use of synthetic engine oils in Mazda rotary engines. Please note that review of vehicle owner’s manuals for the Mazda RX8 shows no warning or note about not using synthetic engine oils. In the early development of synthetic engine oils decades ago, there were purportedly some seal compatibility issues. Today’s synthetic oils do not have the compatibility issues of the old oils. There is no substantiated evidence of seal compatibility issues with Royal Purple.



Here are some facts:

The Mazda Factory racing departments recommend and use ‘synthetic’ oils including the winning 1991 Leman’s 20-G 4 rotor Mazda 787B.
The MazdaComp USA printed manual (now Mazdaspeed) recommends the use of synthetic oils for racing conditions.
Royal Purple Motor Oils have been used in rotary engines (both race and street) for 10+ years with excellent results.
Royal Purple Motor Oil is compatible with the bearing material, sealing elastomers and combustion seals used in a rotary engine.

Here is the response I then received from Valvoline on the same question I submitted to them.

Braden, thank you for contacting Valvoline Product Support with your questions about the use of Synthetic oils in a rotary engine.

The major reason Mazda does not recommend the use of Synthetic oils in their rotary engines is due to this style of engine being prone to burning/consuming oil faster than traditional combustion engines however, you may use Synthetic oil in your rotary engine.

Synthetic oils will not cause any damage to a rotary engine, we just want customers to know that they may burn/consume more oil than they normally would if they were using conventional oils.

If you have any further questions, please feel free to contact us via phone at 800 TEAM VAL or by email at valsupport@ashland.com for assistance.

Thank you and have a great day.
Dave

Now this is the info from Black Halo Racing Rotary Shop
The Great Oil Debate:

Trying to figure out which oil is the best to use in your Rotary is just as impossible as it would be for a piston motor. There are dozens of oil manufactures of which many of them provide their products for various race cars and suggest theirs is the best. Nearly every person has had a good or bad experience with every oil brand on the market. It’s up to you to decide which oil brand to use that fits your needs and budget.

Black Halo Racing’s recommendations on oil are very simple. Stick to a couple rules when choosing your oil. First, ensure its quality synthetic oil and secondly ensure that you use a 5w-30 SAE rating or higher depending on your climate.

Black Halo Racing recognizes that the Mazda manual calls for a 5w-20, non-synthetic, oil to be used in the RX8. Our research and testing as well as various engine rebuilds have shown these suggestions to not be enough to protect your rotary engine. So how is it we know what’s best for your car when Mazda has engineers with PHD’s and millions of dollars at their finger tips?

The reason is Black Halo Racing is not restricted by political or environmental regulations when making suggestions for your vehicle. Mazda, like any other automotive manufacturer, must create a vehicle with operates in all conditions, climates, and also falls within government regulations. The decision to use 5w-20 is mainly environmental and fuel mileage driven. Thinner oils require the motor to work less hard during its operational process. The trade off is less protection of metal parts.

Mazda’s decision to not suggest synthetic oil is due to the inability of them to test fully synthetic oil within the RENESIS motor. Unlike conventional oil, no two synthetic oils are created alike. There are various differences between synthetic oils and Mazda cannot fully endorse one brand over another. Finally, there is no data to show what the long term effects of injecting synthetic oil via the Oil Meter Pump would be. It was easier for Mazda to suggest not using synthetic oil in the end.

On top of this, look at atkins racing, racing beat, Mazda Racing etc. ALL USE SYNTHETICS IN ROTARY ENGINES!

In my opinion, after days of research I have put into this. Synthetics are better than conventional oils for the rotary engine as well. P.S. Mazda MAKES AND RECOMMENDS synthetics in europe and Japan. I've gone to synthetics. It's better protection. As to WHY Mazda would then say to use conventionals if it's actually worse is explained above.

gwilliams6

All these oil debates are valid. i personally used synthetic Amsoil in my past race-modified first Gen RX7. But Royal purple is incorrect when it says there is no Mazda RX8 manual that has a warning against using synthetic oil. My 2008 RX8 owners manual AND owners DVD clearly states IN WRITING and states in voice on the dvd that the owner should NOT use synthetic oil in the RX8. Perhaps earlier Series 1 manuals made no such statements, but the 2008 manual does. The mere fact that it is stated twice would give Mazda legal authority to deny an engine replacement claim under warranty. And unfortunately it has happened to others. For that reason I chose to stick with non-synthetic oil in my 2008 40th Anniversary edition RX8 until my engine warranty is up. Each person must make their own choice over what they perceive as risk to engine wear vs risk to engine warranty. I do premix which gives me some additional internal engine wear protection but doesn't change anything with reference to engine bearing wear.

I respect those that have made to choice to go to synthetics and yes synthetics are recommended and sold to RX8 owners in Europe and Japan. But for American sold RX8s, those Europe and Japanese market differences won't win your case here if Mazda USA denies your engine replacement warranty claim due to your use of synthetic oil. And they have successfully denied such cases in the past. That is the reality folks.