Glyphon

its on page 4-2
and don't worry about the foot in mouth thing. i did that in another thread yesterday :D

Go48

Read what the manual says.

cleoent

my foot is already in my mouth what more do you want ? :D

Go48

BLOOOOOOD! :D

two rotors

I understand from my contacts at MNAO that two major problems have been identified with these failed motors---
1. the 5W20 mtor oil used has been breaking down in the extreme temperatures experienced and a gummy carbon sludge has caused the apex seals to stick and hence loss of compression.
2.Problems with the MOP not supplying enough oil to the apex seals,with consequent accelerated seal and housing wear.
I was told the problems are not related.

I have been using 10W40 (castrol gtx)

zoom44

1. yes exactly
2. they tried a MOP that pumped more oil but it didnt help. the stock pump can flow way more than they have it programmed for anyway.

thanks for looking into it.

rotarygod

It's only breaking down because it's way too hot. That's not the oils fault. That's an oil cooling problem. Chaning oils weights isn't a cure for it.

two rotors

Well it just may be--it depends on the breakdown products I would have thought.Or are you telling me that all oils breakdown exactly the same way?In any event I have been running rotary engines since 1992,including turbos and never had a problem with lubrication.My cars have run in -30C weather up to +50C,4x 10.000 mile cross country trips etc.

rxeightr

So with this diagnosis, what can we do (owners) until MNAO comes up with a fix?

Synthetic?
Higher weight?
More frequent oil changes?

two rotors

Well you have to decide for yourself what you want to do.I have done what I think is best for me.The Owners Manual for Australia I think is instructive.
As I understand it the problem with 5W20 is that it gets more frothy than heavier oils and the gases in the froth are extremely hot and this is why the breakdown,the surface of oil exposed is huge in a foam.It is not necessarily bulk oil temperature which is the problem.But I am sure that some of our resident triblogists can explain it all better.

zoom44

260 degrees is a problem temp for oils froth or not.

bxb40

So it is the damn 5W-20 oil grade.... plus the poor quality probably that make it foam more than other oils (people living in colder climates have a hard time reading the level in winter due to that foam - countless threads about it)........
Now, either use the correct weight for your climate or, if sticking with 5W20, buy aftermarket, not the one dealer use
Now I wonder how much damage my engine has from the first few oil changes (before I started doing it myself and using Castrol GTX)..... should check compresion at some point, I guess. Either if the power will be gone, or just before the warranty runs out.

PS Yes, oils break down much faster from air/oxygen than from pure heat... so the two things above can be related as not all oils foam the same...

two rotors

I assume ,being in the USA,you mean 260deg F.If that is so, your comment can not be serious.There are all kinds of places in an engine where oil is exposed to temperatures 3x that.
I cannot understand how I manged to put all the kms on my previous motors both rotary and piston.Maybe I have magic oil and did not know it!

rotarygod

What will affect oil breakdown more than anything is the exact formulation. In other words you'll get a bigger variance between who's oils you use rather than what weight oil you use. No one should be concerned about 5W20. It is fine. Race teams use the thinnest oil they can. Don't give me the excuse they change their oil after every race. If your temperaures are as high as theirs are, you should too. The problem is with oil temperature. Different formulations may break down faster than others. Just because brand A 5W20 breaks down at X degrees does not mean that brand B 5W20 will break down at the same temperature. Brand B 5W20 may actually break down at a higher temperature than brand A 20W50. You never know. That itself is a problem too because we don't know for certain who's oil is tougher. If you are at a temperature range where this is a large concern, you should be worrying about cooling it back down first and foremost. I run 5W20 in my '84 RX-7 and have no problems. It is supposed to use either 10W30 or 20W50. My oil cooler is also always flowing air through it even at low speeds as the fan shroud also covers it. What we do know for certain is that there are some synthetics out there that don't break down near as easily as dino oils. Among them are Royal Purple which is what I use in my RX-7, Amsoil, and Redline. Some of the other synthetics out there aren't actually synthetics so you need to be careful. That is why Mazda doesn't recommend them. Some are better than others and they don't want to tell you which ones work good and which ones don't. They just give you a blanket statement.

Since the rotary uses oil harder than other engines, frequent oil changes are important. This is obviously because it breaks down faster due to added heat stress. This is true for all rotaries and is not only pertinent to the RX-8. Now compound this with a lack of proper oil cooling in some cars and suddenly the oil breakdown is much faster than normal. When the oil breaks down it leaves a sludge inside the engine. We call this oil "coking". It is what happens in turbos when the oil is not allowed to cool down after being driven hard. The noncirculating oil just sits in the hot turbo and bakes itself into a sludge. This kills the turbo bearings as they don't get proper lubrication. See a similarity? Now ask yourself, is the real oil damage done while your cars are running or is it after you turn them off when hot?

For the most part the oil shouldn't be terribly hot (relatively speaking) as long as it has good airflow to the coolers. The RX-8 doesn't have fans on the oil coolers. Some of them also have only 1 oil cooler which isn't helping matters. Actually these are also the cars that are suffering the most failures. See another correlation? We need proper airflow to the coolers and large enough coolers to do the job. Changing the weight of your oil will ultimately accomplish nothing to fix the problem. It's just too hot.

To demonstrate the importance of rotary oil cooling, look at pictures of the LeMans car or any other purpose built rotary race car. It appears to have 2 large radiators, one on each side of the car. One is an oil cooler. I know it is a race car and is harder on the oil than you are but the fact that it is nearly as large as the radiator should tell you something about oil temperatures. Not saying that you need an oil cooler this large but you get the idea. You do need more efficiency.

What I am saying is definitely true for the single oil cooler cars. The dual cooler cars are far better off. This doesn't mean they can't be improved though.

RotaryGoober

Mazda did cut corners deciding to eliminate the transmission cooler in the 8. Running the lines into the radiator without a secondary cooler keep costs down and temps up. The earlier automatic cars (86-91) ran into the radiator but had a much larger oil cooler and secondary electric fan, as did the Turbo 2's. Bigger IS better when it comes to radiators and oil coolers on Rotaries. I personally liked the 86-91 cooler under the rad. That seemed to work well. The 3rd generation and now the Renesis coolers just look too small to be effective. Unfortunately style and design dictates what the cooling should be instead of designing around the cooling. I guess a Peterbilt front end on a sports car wouldn't lend to a car that would make everyone look at you. It would keep the bastard cool though. ..And just why didn't Mazda pick this up in testing? I scratch my head.

two rotors

Maybe this why the FC3 cars had so many engine problems--one oil cooler,no forced air.

expo1

Would an aftermarket oil cooler be a feasible idea for our 8’s? Mounted in front of the radiator so it would get some cooling from the fan? This would be a very helpful D.I.Y. Looking over how much these cost they are not expensive.

rotarygod

The FC's didn't have cooling problems. The FD's did. There were many contributing factors to this. The FC oil cooler that was mounted in front of the bottom of the radiator also received airflow from the radiator fan.

rotarygod

That particular style of oil cooler is very inefficient. I have no idea why they sell them.

RotaryGoober

Since there is a place for a second oil cooler on the auto shift cars, not unlike the *R1/2* package on the 3rd Generation and now the *8*'s, and the studs are there to mount one. There shouldn't be any reason that the *high* power cooling setup could not be adapted to the auto shift cars. Using an aftermarket cooler would obviously be a help. But I would hesitate to put anything in front of the radiator that restricted flow. If anywhere, mount it where the stock cooler would live. Now to be really slick, one would have electric fans that came on anytime the car would be under 30 mph or so..

jowettw

thanks for your post!!!

helped make sense of the situation for people like me (no real mechanical knowledge but love the car).

demob05

The main issue I'm seeing here is proper cooling, for the engine and esp. the oil. Since the 8's oil coolers don't have the assistance of a running fan like the FC's, what remedy is there for those who drive their 8 as their daily commuter, and like most, may find themselves stuck in traffic jams day to day in 100 plus temps outside?? What benefits will the dual coolers in the 6sp MT RX-8's have if little to no air is flowing thru them in these stop & go situations, looking at it from a long term perspective??

Blue87Sport

Another factor that comes to mind is how much old oil remains after an oil change. I don't remember the exact numbers but several quarts of old oil remain in the oil cooler(s) and lines during an oil change. The old oil remaining is essentially seeing twice the mileage of the oil change schedule. For example, lets assume you replace half the oil during a change and go 3K miles between changes. After the first change, half your oil is new, half has 3K miles. After the second change, half is new, 25% has 3K miles and 25% has 6K miles. Lather, rinse and repeat.

If the oil is breaking down due to high termperature, the longer is is exposed to to those high temps, the more likely the oil will be affected. I wonder if the fact that we're diluting the oil rather than changing it is a factor in the breakdown. Comments?

rotarygod

That could be a contributing factor.

Spyder_doo

The dealer changed my oil once and only once but I requested that they drain the oil coolers and the radiator too and they didnt seem to have a problem doing so.

Jamie