rotarygod

I tried the Pennzoil 5W20 in my RX-7 just to fulfill my curiosity although I'm a bit nervous about it. The results after 2 tanks of gas so far are not a bit of a difference in gas mileage so we can rule out the more efficient part. I was running 10W40 before btw and before that on my other cars 20W50 although I'm pretty much shying away from it. With the 5W20 I have 20 psi of oil pressure at 750 rpm. I can get the engine to idle at 600 rpm and there I have about 15 psi of oil pressure. At 3000 rpm I have over 80 psi of oil pressure. It still easily hits oil pressure bypass. The engine doesn't feel faster or smoother.

I don't believe any crap about the Renesis having tighter bearing tolerances so it needs thinner oil than mine. If there is any difference, it's so little that it's irrelevant. My engine is not smoking at all. Since I have 130,000 miles on my engine and only 10K of them have been since I owned it, someday when I tear it apart it'll pretty much be inconclusive in determining where any wear occurred. I actually don't have an issue with running a low first number in the oil such as a 5WXX or 0WXX. I do think the oil weight should be 30 or 40 though. If the average 30W oil at 100*C is 10 cSt in viscosity, the average 20W is 8 cSt, and the average 40W is 12 cSt, there's only a little bit difference but that's when hot. They get farther apart when they are colder. The fact of the matter is that in my climate (south Texas) it's warm enough all year round that even when my oil is "cold" it's still got enough viscosity that it flows just fine to the bearings and wherever else it needs to go. From a real world standpoint it's not an issue. If we were talking about North Dakota in January then I see the advantage. I will probably go back to at least a 5W30, 5W40, 10W30, 10W40 or so next time around as I can't feel a difference between them and the 5W20 and I know the car has gone at least 130,000 miles on 10W40 and still feels as strong as when new.

ASH8

Taken from 2009 Factory Service highlights showing 04 and 09 8 specs.

441—490Kpa
4.5—5.0 kgf/cm2,
64.0—71.0 PSI

PhillipM

Hmm, that is strange, as my (european) engine goes to over 90psi before the relief valve pops...

ayrton012

That's OK, if I see my european service manual's information, or the new webmesi (service info site) page's data.

5,5-6,6 kgf/cm2
538-638 Kpa
78-92,5 PSI

So there's another thing to look after deeply. Why ASH found different official datas? Was there a change in the production between 2003-2008?

My gauge forces ASH's data (max 73 PSI), but your gauge forces "my" data (max:92 PSI). ???????????

ASH8

Here is some more info, the Pressure Regulator, #3648-14-250 is the same for all 04-08 Series I RX-8's, and is the exact same part used in the 1985-1989 FC RX-7.
Note: 3648 as a model code for this part number dates back to the 1976 Mazda RX-4 13B, in fact it is also the exact same regulator!.

Internally the Regulator has a very common plunger and spring, which dates back to 1967, yes 1967, used in Mazda 800,1000,1300,808. RX-2, RX-3,121,323,626,3,6,929 E series Trucks.

0221-14-115 Plunger Control Mazda RX-8 (S1)800,1000,1300,808, RX-2, RX-3,RX-7 (FC) 121,323,626,3,6,929 E, T, B series Trucks.

0221-14-116 Pressure Spring Mazda RX-8 (S1), 800,1000,1300,808,RX-2,RX-3,626,929,RX-7(FC), E, T, B series trucks

ASH8

BTW, the S1 RX-8 has the same INTERNAL Oil Pump Rotors and Shaft Set (N326-14-140) as the FC RX-7, so therefore the oil pressure specs should be the same (or close to) as the FC.

ayrton012

• An oil pressure regulator has been adopted on the rear side housing to release oil when the oil pressure is 538-638 kPa {5.5-6.5 kgf/cm2, 78.0-92.5 psi} or more.

It comes from the webmesi.

Flashwing

That's the primary heart of the argrument being presented. The normal thought process regarding oil only addresses the oil when it's hot. As you pointed out there are large differences when the oil is cold. So, in theory, if there is very little variation between a 20w and a 30w in terms of flow when warm why wouldn't you use an oil that is thinner at statup?

I have been running Mobile1's 0w-40 for the past 2 oil changes. I had some 5w-20 Royal Purple that was gifted to me so I threw it into the car. I noticed right away the motor was much quieter and sounded much better. There isn't going to be much that can be done regarding the pressure however I think you would agree that if you happen to have X amount of pressure for a particular weight oil that lowering the viscosity of the same oil would yield more flow at that same X amount of pressure.

At least in my case I'm trying to not over complicate oil choice. The primary thing I wanted to get across is the fact that thicker oil doesn't mean it's better for your motor. Also the fact that people feel they need thicker oil because they are doing mad tight JDM street racing isn't the case either. Unless your RX8 is a track monster you're going to be using the motor for what it was designed to handle.

It comes down to how you use the car. A 20w for daily driving will probably work best for me because I have a lot of cold starts.

Fred, what oil are you running in your RX8?

ASH8

Yes, this is the 3648-14-250 Pressure Regulator that I am talking about with the 0221 Plunger and spring, exact same unit and body as the FC RX-7.

In fact ALL Rotaries (apart from 09 Series II RX-8's) have this style regulator on the rear iron housing in the sump.

I am quoting from Genuine Mazda Service Highlights and Parts Manuals, I can't comment on what may be said (or the figures) from "other" sources.

There are no Country/Region Specific Parts for Engine Internals, they are all the same worldwide.

Perhaps there might be slight differences with oil viscosity variations, engine age, I also believe that these plunger type pressure valves are not an exact or precise device, I used to sell
many of the plungers and springs, mainly for Mazda's piston engines, very few sales for Rotaries, even though they are the exact same parts.
The smooth round plunger (or piston) would show micro wear grooves with age.

ayrton012

[QUOTE]
Why a lot of people get more than 90 PSi max oil pressure? That would be impossible, if the 64,0-71,0 PSI regulator open is true. So what?

ASH8

[QUOTE=ayrton012;3142991]As I later edited..

Perhaps there might be slight differences with oil viscosity variations, engine age, I also believe that these plunger type pressure valves are not an exact or precise device.

Just like the Guages that you or others may be using are not 100% accurate?..

So what are you looking for?

ASH8

.....No

Flashwing

There is no doubt some truth to the variations with age. I pull pressure from the oil filter so I normally see around 72-74 psi but I have seen the pressure go as high as 80psi at high RPMs.

It could be an accuracy issue with the gauges as well. I wouldn't obsess with pressures too much except to understand the basics of how it works in relation to oil viscosity and the relationship of pressure vs. flow.

ayrton012

[QUOTE=ASH8;3142997]-The reachable max pressure must not depends on viscosity if we reach our max. pres. at the half of the rpm range, even when the oil is hot.
-Engine age: 28000 miles (0w-30 Mobil-1). It must not be worned.
-There can't be so much difference between the gauge's accuracy. +/- 20PSI?

ayrton012

Yes, the flow is the most important, after that we reach the technically important minimum (reference) pressures.

One more strange thing:
Do everybody of the w20 users reach the 50 PSi at 3000 rpm (factory reference) when the oil is hot?
It seems not (somebody wrote his data). If it's true, how could it be possible, that Mazda recommends an oil weight that not meets their own pressure order?

Flashwing

Not really sure. I notice the same thing. I idle between 20 and 30 psi but small changes result in spikes. By 3000 RPM's I'm almost to 70 psi with the 5w-20 although there is some 0w-40 still mixed in the oil system.

I'd have to look again but those could be minimum pressure requirements and not overall references.

syntheticdarkness

iTrader: (7)

Lots of great info. in this oil discussion.

nycgps

iTrader: (1)

Im thinking the S1's oil pressure is simply too low to begin with. (S1 = Series 1 = 2004-2008 yr model, finally we can use this term like the RX7 guys!)

Just look at S2, they almost doubled everything. Most obvious one is the bypass valve open pressure, exactly doubled.

So I wouldn't worry too much about the oil pressure unless its too low, which I see it quite often with 5w20 after couple hundred miles of use.

and the oil bypass is not really that accurate, its a damn spring ...

ASH8

There is a good reason as to why the S2 oil pressure has increased, the EMOP's.
The engines oil pump now constantly supplies the two EMOP (they are not really PUMPS) call them Solenoid Chambers,oil is also Bypassed back into the sump by the OCV Oil CONTROL Valve.

And the Bypass plunger and spring on the S2 RX-8's is found in the new oil pump assemply...it is not located on the rear iron housing like ALL other rotaries.

9krpmrx8

iTrader: (46)

I wonder what all would be needed to install a series II engine in a first gen RX-8.

Brettus

iTrader: (2)

A lot of determination judging by how much effort went into getting a MT into an AT car ....

ASH8

Lets see..the conversion.

Changing all engine and dash wiring looms, PCM (ECU), need to purchase all the add ons, like the two EMOP'S at $2K, all the hoses, clips, pipes, OCV valve.

Frankly, the cost would be very high, let alone all the frustration, why would you bother, go out and buy a new RX-8.

9krpmrx8

iTrader: (46)

That sucks. My car is in perfect shape so if it were a just a few grand it would be worth it rather than getting into another payment. Sucks its such a hassle though.

Vlaze

iTrader: (14)

There are people here who are over 100k on their cars. I think if you get an OMP conversion it will go a long ways along with using proper oil (0w or 5w) for cold start ups. Or you could have a fluke like yourself, but EVERY model in any brand name has a few that are flukes.

9krpmrx8

iTrader: (46)

Uh, the engine problems are hardly a fluke. And yes there are plenty of people over the 100k mark ( I will be in another few months) but only a couple that I know of that did it on the original motor. We will see when the 09's get up in mileage.