Rotor Rocket

swope, you haven't answered the question yet, but thanks for refreshing my memory re the Star Series.

I'll give you another hint. What is a major component in the street RX-8 Renesis engine that the Star Series or any racing rotary doesn't have, going back even past the 787B of year 1991?

Gotta run out for a couple hours and will log in then.

rotarygod

Mr Yamamoto-san himself. Not Kenichi, he's retired. The current Mr. Yamamoto is the head of Mazda's rotary engine department in Japan. There is no one higher in the rotary engine world than him. Who do you have as a better source than that? Brillo, zoom44, and others were there when we talked on the subject. Every single argument you give is moot. Give up. You lost pages ago.

Don't try to pull the Formula and Star Mazda cars into this. I know what they use and why and chances are I know someone higher in that organization that you do anyways.

Ask Jim Downing or Rick Engman what type of oil they recommend for the rotary. They'll say synthetic. If you don't know who these guys are I'm going to laugh.

rotarygod

This should be good. I can't wait for this one.

swoope

iTrader: (5)

my guess is a mop??? i am out of my element on this one, my first rotary and all...

hope you take the time to read some of his other helpful post on other threads... good for a chuckle...

beers

rotarygod

If that's all it is, that's laughable considering that conventional oils are more likely to cause carbon buildup when injected as they don't burn as clean. Actually that's a blanket statement. Some burn more cleanly than others. The more impurities in the oil the more likely it is to not burn cleanly. The lower the group, the more impurities the base stock has. That's what makes them lower group. They aren't refined or purified as much. Typical conventionals that most people use are group I or II.

Winfree

RG: I am beginning to think you might be correct about using a synthetic - I just ran my first batch of oil - Castrol - and at 2000- miles it looks like tar! This can't be good for the rotar - is there a brand or two of synthetic that you have had good experience with? (I am going in for my first change this week!)

swoope

iTrader: (5)

i did notice that since i switched to syn and running syn premix my tips stay very clean...

but that is just my opioin i could be wrong...

beers

mysql101

So uh... you're going to put this to bed once and for all, but not just yet?

Reminds me of the old joke, "How do you keep an idiot in suspense?"

rotarygod

I've always been a fan of Royal Purple as they have rotary experience and even Racing Beat uses it. There are other good synthetics out there but that is the one I like and use.

swoope

iTrader: (5)

waiting for you to get off the phone with mechanic buddies at Country Mazda in Huntington, LI, NY....

look like something you have seen before????

beers

swoope

iTrader: (5)

this is starting to remind me of The Aristocrats.

beers

toxin440

it sucks to see ANOTHER ******* thread about synthetic....

I use royal purple - been using it for the last 15K miles... more recenly I have noticed my tips dont gunk up NEAR as much (might be my rotary just maturing and getting better with age)

StewyRX8

Ummmm, I was just wondering if I should use synthetic in my rotary? I just sat here and read the whole thread and can't beleive my eyes.

I was only kidding about the question, please don't flame...lol

To steal a line from Mugatu, even my cat searches...

tiggerlee

Dog

Winfree

When you clean and polish your exhaust - do you see more of that fine black carbon with or without the synthetic? (One of the reasons I am considering synthetic is that I don't like the fine black powder which suggests nasty oil burning.

swoope

iTrader: (5)

guess you missed this post:

https://www.rx8club.com/showpost.php...&postcount=132

and yes it is in this thread... killing time waiting for the earth shattering anouncment coming up soon...

beers

MazdaManiac

iTrader: (3)

Don't even bother going for the CAT on this one.
Synth has no effect on the CAT or the HC trap.

rotarygod

This is actually one of the same old threads. 2 of them have been combined to form this monstrosity. The rebuttals are always the same. Nonsense.

(Not aimed at anyone in general) Use what you want. Just don't continue the bs that synthetics are bad for a rotary. They aren't.

rotarygod

Since I'm still awake I wanted to touch on one aspect that hasn't been mentioned yet. This is the only answer that at first sounds like a reason to not use synthetic oils and that is the oils flash point. This too is easy to rebut so let me explain.

I'm sure that RR is trying to touch on this aspect as the only thing that it appears he is going to claim is different between the RX-8 engine and the race engines is as Swoope pointed out, the oil metering system. We will probably hear that a synthetic oil is not good because it doesn't burn cleanly due to flash point temperatures in relation to surface temperatures inside the combustion chamber. Let's first understand the temps inside the engine.

While the exhaust gasses can approach 2000 degrees F, even the combustion chamber in this area of the engine does not reach that high. It sits somewhere over 400 degrees due to heat transfer to the cooling system. The highest heat in the engine being right at the spark plug locations. Those against synthetics argue that conventional oils have flash points that are lower than synthetics and that synthetic oil flash points may be higher than the surface temps inside the engine. This would cause any oil touching the surfaces of the engine to not get hot enough to burn which would leave carbon deposits. Good excuse. Now lets learn what actually happens.

First of all anyone can go look up the flash points of any oil. You'll find that they all sit in the mid to upper 400's to very low 500's in terms of temperature. If you dig deeper you'll find that there are conventional oils that have flash points at 460* and other conventionals that have flash points over 500*. Then you go look at synthetics. Again flash points in the upper 400's and some in the lower 500's. They overlap. No correlation there which could explain one being safe over the other. Both types of oil can have flahs points higher than the surface temps inside the engine. How is there an issue then?

What is the flash point of oil? I'll just provide a direct quote from an oil website since that seems to be the trend.

According to ASTM, which first standardized the test in 1924, the flash point is the lowest temperature at which an ignition source causes the vapors of the specimen (lubricant) to ignite under specified conditions. The oil is said to have “flashed” when a flame appears and instantaneously propagates itself over the entire surface. The oil flashes because a flammable mixture results when it is heated sufficiently, causing vapors to emerge and mix with oxygen in the air. The flash point temperature of an oil corresponds roughly to a vapor pressure of 3-5 mm Hg. When a small flame (ignition source) is applied to the oil’s surface this vaporous mixture will burn momentarily and then extinguish if the critical temperature has been reached. Continued heating of the oil (typically 50-75° F above the flash point temperature) will cause the “fire point” to be reached. As the name implies, the fire point is the temperature at which a sustained flame results (longer than four seconds).

What sticks out about that? How about the flash point being referenced at a certain pressure? It's a pretty low one. How much pressure is in the engine? Depends where we are talking about. That's not the whole story though. Here's some interesting information. Did you know that mineral oils typically start to evaporate long before their flash points are reached while some synthetics do not evaporate until they begin to decompose? Does that sound good or bad? Do you want your oil to evaporate before it finishes doing it's job of lubricating everything? What part of that sounds good? They synthetic will still be there doing it's job. Now I'm sure someone will say that is why they leave carbon buildup. Let's examine a little farther what happens to flash point in an engine.

Fuel dilution plays a huge part in an oil's flash point! The more fuel present, the lower it goes. A mere 2% fuel dilution of the oil can result in a 30*C (86*F)lowering of the oil flash point!!! What is the dilution when injected with the fuel supply? The high level of dilution in the rotary puts the flash point of the oil right down near the flash point of the fuel which is lower than any surface temps inside the engine. How does it not burn again? Suddenly it appears that the flash point of our oil due to a mixing with fuel will now be below what we thought it would be. Far below it! Just because an oil hit it's flash or even flame point and is burned off does not mean it didn't leave anything behind. Remember the oil only lubricates while it is there which is why we need to constantly inject it. We burn off everything we use. A more pure oil will burn more completely and leave fewer and possibly no deposits. Even gasoline will leave carbon deposits due to impurities. Since we know that all oils will hit flash point in the engine due to fuel dilution, they all burn. However the more impure oils such as the lower grade conventionals will have more leftovers of the process that didn't get burned completely. This shows up as carbon deposits. The higher grade synthetics will burn completely leaving little to nothing behind. This is one big reason why I like synthetic oils. They have fewer impurities which can be left behind. Group I-III oils are conventionals. The lower the grade, the more impurities left behind in it. If you insist on conventionals, which one would you want to use? For crying out loud use a Group III! Why do most people use Group I-II oils? A couple of bucks difference in price? Better have a better excuse than that. I've seen people not want to use Group III's because they claimed that the only difference is that it is "more refined". DUH!!! That's a good thing moron!

A little side stepping here. I ran an experiment last year with several different types of oils. It was on the premise that some didn't mix well with fuel and that this may be the issue with the oil metering. Every oil conventional and synthetic mixed and stayed mixed. They never separated. I still have the test vials full nearly a year later and they are still mixed. That's not this issue. If there was an issue with oil metering, it would be based in surface temps and burn ability inside the engine and I just shot that one down but telling the whole story rather than part of it.

And that as they say is that...

Paul_in_DC

Which royal purple do you use?

nycgps

iTrader: (1)

I used 5w20 before, RP, Advance Q, and Castrol Syntec. All Full Synth of course.

I just switched back to RP's 5w30. So happy (my rotary, I mean,revs smoother and less black thing on the tips.)

Might try 10w40 later, but ahh, think about it.

and RR, you're going to lose, stop trying and move on

PeteC

Hey RG....sorry if this has been covered before but since you've done all the actual experiments (thanks) I figured I'd ask.

Everyone seems to keep making a correlation between sooty exhaust tips and oil consumption. I don't remember my RX-7 having this problem but it's been a few years. I've got a lot more current experience with highly tuned two stroke motorcycles. Not a rotary I know, but engine tuning has lots of consistencies from two strokes to rotaries (hell even to 4 strokes).

Any time you're tuning a bike a sooty exhaust is a clear sign of the engine running rich. If you're running oil at a heavy enough setting that it's not getting burned it can actually drip out of the pipes but it doesn't leave the dark, dry sooty residue that I see on my 8.

So here's my question, have you (or anyone) changed the fuel mapping of a Renesis motor to run leaner? If you have, did it clear up the sooty tips? If so this would indicate to me that for some reason (emissions? longevity?) that Mazda intentionally set the motor to run way too rich. Another plus of this would be that a leaner mix makes more power.

Any thoughts?

nycgps

iTrader: (1)

As far as I know Mazda made it rich for emission reasons.

so .... let RG handle the rest :D

dastallion951

ok its quite simple, all u convention fans, can keep runnin ur dino oil, us synthetic users will be usin ours, n when ur on the side of the road becuz u blew a seal becuz ur conventional couldnt handle the repeated use of high amounts of heat, n ur engine is totalled..........maybe u shouldve realized hey i shouldnt have been so ignorant n listened to people who know what there talkin about with rotaries........not people at mazda who are just tryin to make money off of u.......but stop the arguing........run the conventional.......just hey take ur aftermarket parts off becuz hey they void the warrantee if theres a problem......but SYNTHETIC is a BIG NO NO. lol (some people r so retarded)

brillo

provided you use a good group III dyno oil and you change it every 3K, you should be fine, I don't want dyno oil users thinking they are going to blow their seals, thats far from true.

I run premix when doing any kind of harsh driving, which I would also recommend for dyno oil users if they hit the track, auto-x, etc...