Why should I not use Purple Royal 5W-30 synthetic oil in my 2009 RX-8 with 35,000 miles on it. All the tests I have seen show Royal Purple to be one of the best performing oils you can buy.

Should I use it?

 

You can use what you want but I suggest reading the oil reports for Royal Purple in the in used oil analysis thread. Paimon had a few tests done by Royal Purple after the results from the test he did were not so great. The tests done by RP themselves essentially showed the same thing. It's not a bad oil, just not as good as it is hyped up to be.

Royal Purple is great at marketing though.

 

Castrol FTW

 

if you want 5w-30 RP, use their 10w-40 ... trust me it'll break down to a 5/30 in no time lol.

it took me receipts and constant affirmation to prove to them that i did indeed send them samples of 10/40

 

It won't hurt your car, but it isn't worth the money either. Mobil 1 performs better and is less expensive.

 

Qft

 

Define better. Durability? Varnish resistance? ZDDP content? Film shear strength? Combustion products?

For track? For regular driving? For cold weather?

There aren't simple answers with oil

 

The test reports I read from an independent lab showed Royal Purple out performed every other brand. Mobil 1 performed worse than Dino oil when came to film strength and scoring. Both Dino and Synth. I don't drive the RX hard. I probably split equal time between highway and around town driving. Once in a while I'll run the engine up to 7-8k rpm. If not Synthetic, then what is the best Dino?

 

The closest thing to a consensus on oil in this gang is that the type and brand don't matter as much as changing it every 3000 miles. If you're racing or have a turbo then I'm sure the type matters, but for a stock 8 with normal street driving it's not a big deal.

There does seem to be a partiality toward Castrol. I've been using it in all of my cars for half a century, and use it in my 8. I can't give you a rational reason, but I feel comfortable with it.

Ken

 

Link to the study?

Here is one from Amsoil from 2013. It basically says Mobil 1 sucks in a lot of areas too--especially in the area of wear. It also shows Royal Purple to be very mediocre, performing about as well as Valvoline Synpower and Penzoil Ultra at a much higher cost.

The question is, how do these oils stack up in our engine in the real world? It is nearly impossible to know. What we do seem to be able to correlate in the UOA thread, is that 0W40 Mobil 1 performs quite well in our engine, and RP does not perform as well as less expensive options. That is why I said it is not worth the money. The reality is that it doesn't much matter what you use as long as you change it frequently.

 

Castrol has been the dino oil of choice for rotaries since the 1970's. Mazda dealers started using Castrol in their dealer network for oil changes way back then and many Mazda dealers continue to use Castrol oils, both dino (rotary Mazdas) and synthetic (piston Mazdas).

Again use the oil you wish, there has never been a consensus on oil type. Just know what you are getting and change it every 3000 miles, because you only drain half of it anyway , the rest stays in the oil coolers. So being diligent on oil changes gets that used oil cycled out of your car sooner.

 

The more time you spend worrying about oil brand, type, or weight, the less time you have to worry about all the actual ways your engine could fail.

 

BTW I used Amsoil full synthetic in my race rotaries ,including my 400 hp one built by Racing Beat back in the 80's. But that race-ported, turbo and intercooled rotary was running high boost and high load almost all the time, and had special apex seals , with low-compression racing rotors to take that boost and stress .

As RIWWP says , your oil choice would only effect your eccentric shaft bearing wear, and even there we only see failure here in extremely rare cases. Your oil choice would not be an actual cause of engine failure. Your oil, even though it is injected in small amounts to lubricate inside your engine under load, its main purpose is in helping your cooling system to keep your engine safe. Any oil viscosity of proper weight for your climate and driving habits is fine, dino or synthetic. Just change oil regularly ,every 3000 miles is best.

 

Castrol is owned by bp who is owned by morgan stanley. They make the rules in our country and can tell us what oil is best for us. Castrol is the best known name for 5/20 non synthetic. Doesnt seem so far fetched to assume that is why we are told to use that in our country. Use what you want and change it often.

 

Rotators require extremely specific types of oil and it needs to for extremely precise criteria or else the apex seals. Here they are, gathered from 47 years and 7 rotaries of experience:

A) It's oil
B) It's in the lines/sump/coolers/engine
C) It's hot
D) It's not too hot

Seriously, it doesn't matter, you're burning a good amount of it anyway.

 

As I said before, like clockwork Legot always follows my post. Hmm I don't know whom you mean with 47 years of rotary experience, I only have 42 years in rotaries, and I agree with you Legot, or did you miss my quote above "Any oil viscosity of proper weight for your climate and driving habits is fine dino or synthetic. Just change oil regularly, every 3000 miles is best."

 

Mazda dealers don't specifically use Castrol, they use whatever they get cheapest. I have a thread here somewhere, but I went to the local dealers after a local member and tech told me his dealer did not use 5W-20 and took pictures of their oil tanks and they all used different oil in brand and weight. One was Mobil Super 5W-30, one was Valvoline Conventional 5W-20, and the dealer I frequented used Castrol GTX 10W-30. So if a dealer ever gives you **** about oil, walk around the back of the shop and see what oil they have on the tanks.

 

Just for fun...here is my oil rant

The only issue I ever had with oil is running out of it ( funny how cornering does that when the oil pump sucks air)

Change it when it needs it....the new oils last a hell of a lot longer than 3K miles

Make sure you use a good filter

The 5/20 is too light for a rotary....Personally I love the 5/40 synthetic that i have been running for years

Most good brands of oil will perform very well......don't think though that the amount of money they spend on fancy advertising has anything to do with how good the oil is

You would be surprised at how few places most of the base stock for these oils come from anyway

If you really want to get your head spinning...check out the " Bob is the Oil Guy" forum...more info there than you would ever want to know about oil Used Oil Analysis - Bob is the Oil Guy - Bob is the Oil Guy

 

This debate and discussion is endless........................................... .................................................. .....

 

[QUOTE=9krpmrx8;4685451]Mazda dealers don't specifically use Castrol, they use whatever they get cheapest.

On the East Coast many, many Mazda dealers still use Castrol. I never said ALL Mazda dealers, which of course are all independent businesses. But the history of Mazda and Castrol does go back decades to the seventies, before many of you were born.

 

Yes all manufacturers have relationships with oil brands and it means nothing.

 

You are free to interpret the facts of Mazda's and Castrol's business history together anyway you like. This is an oil discussion in the Mazda RX8 forum.

 

Yes, so what is your point?

 

Just responding to your rather pointless post, that's all

 

Thank you everyone for the lively and interesting points. I bought Royal Purple already and a K&N Oil filter which I'll use for me next oil change. But make sure its changed at 3K.

So my next question is if the rotor motor uses about a quart every 1000 miles (which mine is right on that mark) by 3000 miles, you will have already replaced 2/3rds of the total oil, what is the point of a complete change at 3K? Basically, the engine will always have fresh oil. If you change the filter every 3K, that is probably at least another 1/2 quart. Which by my estimates means the engine pretty much always has fresh oil. What am I missing?