Royal Purple's view on synthetics in the rotary engine
 

I didn't see this anywhere else so I apologize if this has been posted already. Royal Purple added a section to their FAQ page that deals specifically with the rotary engine. I'll just copy and paste it below.



"Rotary Engines

Can Royal Purple Motor Oil be used in a rotary engine?

Yes. A rotary engine is a modified four cycle engine that recommends the use of an API licensed motor oil for street applications.

More information and FAQs on lubrication of Rotary Engines:

In a rotary engine, the oil lubricates the eccentric shaft bearings, thrust needle bearings and rotor bearings similar to a crank and rod bearing of a piston engine as well as being injected into the combustion chambers to lubricate the apex seals, corner seals, and side seals helping to create the sealing mechanism doing the equivalent job of the piston rings.

Royal Purple provides outstanding protection for the e-shaft, rotor bearings, thrust bearings and is suitable for the oil injection system as it has proven to run cleaner than other oils and is an excellent choice for rotary apex seals, corner seals, and side seals.

Mazda makes a statement in the Owner’s Manual not to use synthetic oils in a rotary engine, why do you say that it is OK?

Royal Purple has performed seal compatibility testing on the components used in a rotary with excellent results, including older rotary engine seals dating back to the Cosmo. Royal Purple’s Technical Services Manager David Canitz has been an owner and racer of rotary engine cars and has used synthetic motor oils in rotaries since 1985 with excellent results. He has been trying to find an answer to this Mazda statement for the last 18 years.

In the early development of synthetic 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 26B 4 rotor Mazda 787B.

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 ten plus years with excellent results.

Royal Purple Motor Oil is compatible with the bearing material, sealing elastomers, and combustion seals used in a rotary engine.


I heard that synthetic oil doesn't burn like mineral based oils and will coat the inside of the engine with deposits.

If this was a problem with synthetic motor oils in general, then all internal combustion engines using a ‘synthetic’ would experience increased deposits on internal surfaces. The opposite is actually the norm.

Conventional four cycle motor oils will typically leave deposits of carbon and ash when injected into the rotary apex seal, corner seal, and side seal areas. Royal Purple’s motor oil actually burns cleaner due to the synthetic base stock being free of contamination and many of the additives being ‘ashless’. This may not be true for all synthetics but Royal Purple has been proven to work extremely well in rotary engines.

Royal Purple’s formulation of synthetic hydrocarbon motor oil does burn at the nominal combustion temperatures experienced in both street and racing applications, whether normally aspirated, turbocharged, or supercharged. (500 – 1700° F idle to race rpms typical combustion temps)

Will the synthetic oil effect the oil seals?

No. Royal Purple’s Motor Oil is fully compatible with the elastomers found in rotary engines as well as more conventional piston engines. The oil seals, housing seals and other elastomers used in rotary engines typically consist of Buna N, Nitriles, Neoprene, or Viton materials which are also commonly found in piston engine cars.

I hear that synthetic is ‘thinner or lighter’ oil, is there a greater possibility that the oil will leak between the seals?

No. If an engine’s sealing surfaces are in good condition, synthetic oil should not cause any leakage. However, if an engine has marginal seals, there is a 50/50 chance the seals will leak less or more. A synthetic motor oil is going to have similar viscosity to that of a conventional motor oil – except at extreme temperatures. Due to a flatter viscosity curve, at low temperatures it will not thicken as much (easier winter cranking) and it does not thin out as quickly at higher operating temperatures (better oil film at higher rpm).

Should I go longer or shorter between oil changes?

Royal Purple recommends that the maximum oil drain / filter change interval listed in the Owner’s Manual be followed while under warranty (new RX8). For SA, FB, FC, FC Turbos, and FD rotaries, extending drain intervals from two to five fold is possible if desired. Since the rotary engine injects oil through the use of a metered oil pump, either adding oil into the carb base plate air / fuel mixture or directly injecting oil into the rotor housing, rotary engines will consume oil of one quart per 1000 – 3000 miles. It is important to maintain the proper crankcase oil level in your rotary engine if you decide to extend oil drain intervals.

If I pre-mix my fuel for the rotary engine, do I use the same ratio as with mineral based oils? Does it burn at the same rate?

In an ideal world, the rotary engine metered oil pump should inject an ashless oil designed to burn in the combustion chamber and use a four cycle oil in the crankcase for the eccentric shaft, rotor bearings, and thrust bearings. For the street, Mazda simplified the OE system to use just one oil, that being a typical four cycle oil for both the e-shaft as well as the combustion chamber. Royal Purple recommends using our standard TCW III 2 Cycle Oil if the metered oil pump is still enabled. The two cycle oil being added to the fuel tank is in addition to what Mazda designed to inject and acts as a supplement or insurance. Depending on which engine, the level of modifications (street port, Bridgeport, peripheral port, nitrous, turbocharged) and application, the typical mix ratio could vary from 200:1 to 800:1.

For a pure racing application where the metered oil pump has been disabled or removed, again based on the actual engine and modification level, the ratio could vary from 150:1 to 600:1. For this application, we recommend our Racing 2 Cycle TCW III product or the standard 2 Cycle TCW III can also be used.

A stock FD twin turbo 13B with the MOP oil injection system can typically use about one quart per 1500 miles under hard street driving. If this vehicle is getting 15 mpg, the gasoline to oil ratio is 400:1. If the oil consumption on this vehicle reduces to 1 quart per 2500 miles and fuel efficiency increases to 20 mpg, the gasoline to oil ratio increases to 600:1. The stock metering oil pump is a great system as it varies with throttle position (load on the engine). Pre-mixing has to be calculated for the ‘worst case’ that will be seen by the engine for that fuel load. Under racing conditions, that’s wide open throttle at racing rpms. This means that at idle, the ratio may be slightly fat (rich)."




I think that about sums it up nicely! Thanks Royal Purple!

RG

Good stuff....
 

Some good info there, I hadn't seen that.....
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doc

As taken from this source :

A special synthetic oil was developed by Idemitsu Kosan Co. just for the Le Mans race. It has a polyalphaolefin base with a detergent inhibitor package and a molybdenum friction reducer. A street version of this oil called "Rotary 1", meeting API specifications, became available in 1996 in 1-liter and 4-liter tins painted like the Le Mans winner. Be warned that it's incredibly expensive: $38 per LITER (1999) or $133 for 4 liters.

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Unfortunately the links for this oil aren't working anymore.. I wouldn't mind having a can with the 787 color scheme just for decoration! :)

Excellent post. Well-reasoned and backed with facts (something all posts don't do) :D

Thanks for the info. This should put the issue to bed.

So, where do you guys find Royal Purple?

gee, I remember arguing the fact that synthetics burn cleaner and give better protection for a good 6 months or so now...

aside from the cool ass can, theres nothing unique about the oil once you decode the buzz words...

a "polyalphaolefin base " is a normal group IV PAO synthetic base stock, a "molybdenum friction reducer" is just an ordinary friction reducer package most manufacturers use, and it has a detergent package like everybody else....


if only a company would get serious and make a real rotary oil - an oil that gasoline isn't soluable in, will resist foaming and water retention, and offer great wear resistance... unfortunetly I know a formulation that was this, but never made it past the beancounters at a particular oil company... maybe one day :mad:

Here in Fort Lauderdale Speed and Truck World carries it. There's a guy on Ebay who sells it cheaper though, even with shipping factored in.

One thing I don't know...does RP make the specified weight for the RX-8?

jds

Yes, they make 4 cycle 5w20... either for race or street.

Napa Auto Parts carries Royal Purple now (in California, at least).

I originally posted this on the Australian Forum. Someone pasted it on the Tech garage forum, but I'll add it here for those who have yet to read it....

Finally got an answer to this age old question, and an official answer at that.
I have a copy of a parts bulletin, distributed to all dealers, for circulation to Dealer Principal, Parts Manager, and Service Manager which reads as follows: (Sorry, can't copy it onto the forum yet...technical issues!!!)

Dated 17-9-03!!!!!!
Quote:
Due to some misunderstandings in the field in relation to the use of Synthetic and Mineral oils in rotary engines, National Technical Dept have created this Tech Tip in order to assist your staff with enquiries.

Pre- Renesis:
All Pre-Renesis engines have a set of oil control seals in the sides of the rotors, which are designed to keep oil from the lubrication system out of the combustion chambers. Each seal consists of a metal scraper with a rubber o-ring within.

MC advise this o-ring is not compatable with synthetic oils (or synthetic/mineral blends) and that such oils can attack the material in o-rings, causing them to break down and deteriorate. Should this occur, excessive amounts of oil would be drawn into the combustion chambers causing high oil consumtion, smoke from the exhaust, fouled spark plugs and reduced engine life.Therefore, synthetic oils or blends are prohibited and only mineral oils must be used in early rotary engines.

Renesis engine:
This engine has similar seals, which perform the same function as with the Pre-Renesis engines, however, the o-rings are constructed with a completely new type of material that has improved longevity and compatibility with synthetic oils.

While such oils are not prohibited from being used in this engine, MC still advises that mineral oils are more suitable for these engines. This is why MA will be importing mineral based 5W30 engine oil.

Genuine MC Engine oil for Rotary Engines:
We are currently in the process of sourcing genuine MC oil from Japan. This is a straight mineral oil with a viscosity of 5W30. There is quite an involved process to import this oil and then decanter it, which is the reason for the delay in supply to dealers. When available, this oil will be dedicated for rotary use, whether Renesis or early models and only available to the parts departments of our dealer network in 5 litre and 1 litre packs.

We will advise part numbers as soon as stock is available for sales.

Aldo Schepis
Part Business Manager.
End Quote.

Guy's the key info imparted here IMHO is the use of the words "improved longevity and compatibility". Mazda know their engine better than ANYONE, if long term durability isn't an issue with you, pay more and freely use a synthetic! BTW, Mazda Rotary Oil is now avail in Oz @ AUD$55 for 5Ltrs....Its been decantered into a Castrol container.

Regards, Gomez.

I wish Royal Purple and Mazda would just don the gloves and duke it out. Someone should do a test that proves squarely that synthetic oil eats these seals and o-rings. I personally don't believe it, and have seen plenty of anecdotal evidence that it does not, while seeing nada to imply that it does, save statements like this. Sorry, I'm just not buying it. That said, I'm not convinced that the benefits outweigh the risks, especially in a normally aspirated motor like the Renesis.

jds

I've used synthetics in my RX-7's and never had any seal issues. I know several others that have too with no problems. It just sounds like Mazda needed an excuse and figured that a majority of the people would not have experience with synthetics and the older engines and would believe this. Remember they used synthetics in many of their race cars including the LeMans 787B.

I have sheduled a dyno session on Thurs 4/22/04. I have baselined the car at 1000miles. I just installed Stage 1 Canzoomer mod and want to test it. The big reason is b/c I was invited to test [before and after] royal purple in my car. They claim it will increase HP and protect the engine better.

We shall see.
I expect to do several pulls:
1. With the 5W20 or whatever Mazda puts in it - CZ1 off.
2. ...CZ1 - ON
3. Change to Royal Purple, CZ1 ON
4. Royal Purple CZ1 OFF

That will be great. Not only the first independently published dyno runs of CZ stage 1, but pulls before and after the purple stuff. Look forward to seeing your results!

Racing Beat noted an increase in horsepower in the RX-7 when using Royal Purple, but I wouldn't expect anything major. It was noteworthy in that there really should be no expectation of any power gain. I don't know what your expectations are exactly, but I doubt this will be considered a major power adder

jds

I think you'll find just about all manufacturers use the word "compatablility" with respect to sythetics. I'm sorry, but your editorial "HO" looks like reading more between the lines than what's there, amounting to yet more FUD.

I can see that if you're inclined to be in favor of non-synthetic you can take comfort in this interpretation; similarly, those that believe the oil analysis and wear testing results showing synthetics provide superior performance in every way can also take comfort with that very same statement from Mazda.

Like Gordon oft points out at times like this, the manual states the specific oil weight and API requirements only -- something quite different from previous editions.

Also worth pointing out - that's a nice Mazda Australia blurb, but note they specify 5W30? Mazda North America specs 5W20. Mazda's recommendations are not universal, they vary region to region. Mazda Europe uses synthetic for their dealer oil changes!

That said, I fail to see how any characteristic of synthetic makes it less suited to a rotary... better oil is simply better! ;)

Regards,
Gordon

Those who can't see the forest for the tree's, are sure to bump into them, IMHO.... !!

Gomez.

I too will be very interested to see these results. Please start a new thread here when you post them.

Re: Royal Purple's view on synthetics in the rotary engine
 

Wow.. didn't realize this (non) issue was THAT persistent :D Lol.

Wow - not soluble with gasoline, AND doesn't retain water? that's a tall order. What kind of substance was it?

I run RP Racing 21 oil and have had zero issues ;)

The idea to test with dino oil, then RP is a good one in theory, but unless you're planning on draining your oil coolers between runs, (which will almost certainly lead to leaks) I'd say that's gonna be tough to do.

That being said, I've been running RP 5W-20 since my first oil change, and it seems to run quieter now. It uses the RP at the same rate as the dinosaur, (about 1/2 qt every 1,000 miles), and I have not noticed any ill effects, nor any good ones other than the "percieved" drop in mechanical noise from the motor (which as we all know, is most likely mental).

If it's good enough for Racing Beat and good enough for a 727B enduro car, it'll do for my little Renesis. I ran RP in both my SC'd Miatas for 5 years, never had one complaint. It's the cheapest peace of mind I can buy.

Well the difference is that Mazda reccomends it for racing applications. That would leave me to believe that with our fuel maps that they thought some synthetic would not burn or leave deposits for drivers that don't rev the car. But then again they do allow synthetic in other countries and RP says that it burns very well. I am thinking of trying it but I am still a little skeptical.

so is what RP said apply to ALL synthetics? or JUST RP? I can't find any dealers of RP near me

nothing to do with deposits.....all to do about oil seal o'ring longevity.

Racers don't care about longevity, longevity to a racer is measured in hours. If you measure longevity in years, use a mineral oil.

Gomez.

Here's why.....Page 1....

...and page 2....

That's a complete steaming pile of bs that Mazda printed up. NO synthetic currently on the market will have any adverse effects on the older rotaries seals. That sounds like a lame excuse to justify the confusion. They also seem to be hoping that the current rotary owners will not have any previous experience so they can get away with saying these stupid things. Their statement may have applied to the early synthetic oils but definitely nothing currently. I have used synthetics for years with no adverse effects.

It's funny how no one believes Mazda when they state horsepower numbers for the car, yet people quote them for other things. It's all or nothing. Believe them or don't. I personally know for a fact that the engine will be fine with synthetics. I've done it. It doesn't mean that they are necessarily any better, just that they will work and cause no harm.

If an oil has a rating on it and the vehicle manufacturer has stated that oils with this rating are suitable for their vehicle, it doesn't matter what type of oil it is. Mazda recommends synthetics in europe. As much as I hate to say it, there is nothing special about the U.S. that would make oils or cars here any different.

Your average everyday synthetic oil is just fine for the Renesis - use Castrol Syntec 5W30, or Mobil1 5W30, no problem. If you can find synthetic 5W20, use that! Make sure it's API SL, though.

Regards,
Gordon

cool I can only find 0W20 form mobil1 but it says "forumulated for 5w20 applications" so I'm putting some in tonight
will let you guys know if it blows up :D

LOL this is great, from knowing about cars till now I've NEVER guessed owning an RX8 would let me into these privileged discussions :D I mean, HOW MANY ppl can tell you they can have so much to talk about their cars just with the type of oil (never mind what brand) :p

I'm new at this Mazda game, this is my first rotary....For what reason would Mazda have a bias against synthetics?

Mazdaspeed market a synthetic that they used at LeMans in their racers to great success.

You, I assume have owned a number of rotaries, and have had no problem with synthetics......How many cars though? Ten....Twenty?

Your mates have owned another hundred?

Mazda have produced hundred's of thousands of these things....

The data that they have collected over 30 odd years of rotary production should allow them to make the claim that a synthetic is no good for long term applications....O.K for a racecar that needs extreme protection in a high stress, high temp, short term environment. They get rebuilt each race.

So why believe Mazda have it in for synthetic oils, they sell the stuff themselves in a Mazdaspeed tin!

Gomez.

Dear Rotary God, could you please explain why the letter by Mazda is a steaming pile of BS? You seem to only explain that you personally have had no problems with synthetic, this is hardly confirmation to suggest synthetic is best for the 8 -
please elaborate why synthetic will not harm the apex seals.

Their paperwork suggests that synthetics are not compatible with the older rotaries. I know this to be untrue. Maybe if you go back to the '70's but not with the RX-7's. I have used synthetics in my past rotaries with no problems. I have also rebuilt my own engines and found no adverse internal effects. The rebuilds were not due to dead engines but rather from a porting standpoint. Their paperwork actually suggests that synthetics will work fine with the RX-8 and there is no reason why it shouldn't.

While I have used synthetics in the past, I actually prefer good oil dino oil. This is solely based on price. As far as synthetics go I am a fan of Royal Purple and Amsoil. I also know better than to believe the hype about 3000 mile oil changes.

Personally I don't care who uses what in their own cars. It really doesn't matter to me. Synthetics work just fine. Why wouldn't they? The do not eat rubber seals.

So many RX-8 people use terms like "it doesn't say that in the manual" and other excuses. The manual also doesn't say to replace your intake with a K&N. It doesn't say to replace your exhaust system or ecu either. You guys don't believe them at all when it comes to the car's rated output of 238hp and get mad at them about gas mileage. People constantly complain about dealerships not using the recommended oils. After all of this why in the hell does anyone believe what they say when it comes to synthetics? There have been many independent tests done over the years. There are also many rotary owners that use synthetics.

So many people don't believe the words of the people that have done it and found it to work yet they believe the people that they accuse of lying to them about other aspects of the car (Mazda?). The problem is obvious to me. Where's the issue?

Personally I don't really care what others think. Synthetics work fine in the rotary. Myself and many others have done it with no issues. Don't you honestly think that there would be a large number of people that would post negative info about synthetics in rotaries if there were problems? It would be all over the internet but it isn't.

Just to shoot down the remark about me only knowing because I must have owned hundreds of rotaries and that Mazda should know better, here's a little info for you. Yes, they do know their car better than anyone but the Renesis is capable of much better fuel mileage, much more power, and still retaining the ability to pass all U.S. emissions standards. Shouldn't the people that designed and built the thing already know this and shouldn't they have already done it on the production car? Is there a possible reason why they are constantly giving us new ecu maps if the original one is the best it can be? Remember they should know the best. Don't they know why their car floods easier than others? If they are so high and mighty, wouldn't the all knowing powers that be have provided us with the most reliable vehicle around? You still believe everything they say? I'll leave it at that.

When I was trying to decide if I should use synthetics in my FD, I asked around on the RX7 forum and various other places. Lots of people will pipe up and repeat all the hearsay. I found only ONE person who had ANY direct personal experience that had even a remote chance of being associated with the oil, and that was back in the early '70s. More surprising was the large number of people who admitted to using the synthetic stuff...in many cases for years and years, some haveing torn down engines for comparison purposes, etc. They didn't jump in every time the topic came up because (and I'm starting to get this feeling myself) it was too annoying to hear the same unsubstantiated BS given as reasons for not using it. So, they kept using it, quite happily, and stopped paying attention to the threads discussing it.

The only thing that might make me not want to use it when I get an RX-8 is that I'm not sure the benefits are substantial enough to outweigh the cost differences. For the FD, turbos put a huge stress on the oil, but for a normally-aspirated car...the benefits would seem to be less.

jds

Also worth noting - that Memo is NOT from Mazda Corporation, it was published by Mazda Australia, one of their regional companies. It's no different than Mazda North America or Mazda Europe offering different opinions...

Regards,
Gordon

Hang on, read it again.......it clearly references MC in the memo.....in fact it says Mazda Aust is importing Mazda Corp Rotary Oil....that memo is drafted on advice supplied by MC.

Gomez.

Didn't the RX-7 have a decal under the hood advising against the use of synthetics, even the late series????

Lead me to these independent tests, I'd like a read......and I still have yet to hear a reason why you all believe Mazda have a vendetta against synthetic oils.....as I said before, they even market and sell the stuff for racing applications!!!!!!

Yours in anticipation, Gomez.

Perhaps it's not a vendetta against synthetics. Maybe one car out of a thousand has failed over a ten year period due to synthetic oil, and Mazda feels that that warrants them putting the statement about synthetics in the manual. If that's the case, I'd say synthetics are fine, but I'm still going to obey the manual, more out of habit than anything else.

rotarygod, I assume you rebuilt an RX-7 engine after using synthetics? I understand that you found no incriminating evidence against the use of synthetics, but out of curiosity, how long did you drive the car? A 200k mile rotary run on synthetic would seem to justify that synthetics work fine, IMHO.

Probably at least one of two things is at work regarding their "vendetta":

1) The dealers want to sell oil changes. From what I understand, this sort of minor thing is the service departments' "bread and butter". Synthetic = fewer changes = less cash. In Europe apparently, people are already used to 6,000 mile oil changes.

2) The RX-8 uses about...1/2 a quart every 1000 miles (?). So with a 3.7 quart capacity, it only takes 6,000 miles (or less?) to get dangerously low on oil. Mazda may be covering their butts against people who buy a quart of synthetic and think they can go 6,000 - 12,000 between oil changes because it says so on the bottle.

Gord--would you happen to have a copy of the European service manual scanned, where they specifically say synth. is ok? My dealer didn't give me any trouble last time but if they ever do, I'd like to have that in my glovebox. :D

Hmmmm, Mazda set their service intervals....they could have specified synthetic and a 4500mi period and milked it for heaps!
A bigger margin on a more expensive oil.....

On point 2, their out if someone tries that on is in the Owners manual....the copy of the U.S manual I have states changes at 7500mi for schedule 1 , and 5000mi for schedule 2 (which I reckon most U.S drivers would be operating to.....)

Also, your manual recommends a check of the oil level each tankfull.....(ours says each week).........

I realise you sometimes can't protect people from themselves, though!!!

Gomez.

Did he ever post the results? I didnt see a thread on them...

Ooops, I forgot.

The RP vs. mineral dyno indicated a few hp increase on my car. The oil was changed on the dyno so we did non disturb the setup.

I have been using RP since David donated a few oil changes to me for the dyno and RX-8 time. The dyno data is on my home PC. I will try to remember to post it. My CZ unit was not doing so well that day and it distracted me from the original purpose of testing the RP product.

Always used syn and just put some Royal Purple in.

i don't buy a blanket statement that some thing is not good without some details as to why. and mazda have not provided any documentation anywhere as to WHY syn should not be used in the 13b.

As RG stated syn oils meet the same specs as DINO and that's what matters, but they also have a better performace range. hence the benefits.

many manufacturers recommend syn from a factory fill, especially on hotter running engines like the sti and evo.

BTW, i also put a drop in K&N tonight as well :)

For those interested, I just passed 17K miles on the RP, and then engine hasn't destroyed itself yet. :cool:

oh but it could go at ANY MINUTE!! :rolleyes: ;)

Yeah, they have....and I posted it earlier in this thread.

OK then, let's put it this way: Mazda has provided numerous bits of evidence which directly or indirectly indicate their opinions both pro and con with respect to synthetic oil and rotaries. They're the John Kerry of the automotive world! :D

jds

PS: Since I know someone will ask...there was the article provided by Gomez on the con side, and the fact that they actually recommend synthetic in rotaries in some parts of the world on the other. There have been other contradictory statements and actions as well but you'll have to do your own search to find them.

Hahaha, but hey, JK is a war hero....lay off him!