Interesting formulation strategy? Idemitsu Rotary 10W-30

[d00df00d]

Been doing some general research on this oil for my RX-8, and I think I found some things that might be of interest more generally. I want to first lay out some of what I've found, and then offer my interpretation for feedback.

The oil:

Idemitsu Racing Rotary Engine Oil (10W-30)

It’s a PAO-based 10W-30 with some ester content. Supposedly optimized for rotary engines, but I wonder if it might be useful for other engines as well. More on that below.

Got some unpublished info on it from Idemitsu (HT Marlena):

- HTHS: 3.46 cP
- 600-800 ppm moly as MoDTC
- Sulfated ash: 0.88%

How often do you see an oil with that much moly and so little sulfated ash?

I looked for UOAs and VOAs for more details, and found only this:



(Clipped from this post: https://www.rx7club.com/3rd-generation-s...3/#post10754140)

Looks like a moderate amount of ZDDP, a fat slug of moly, and a very moderate amount of Ca. Little or no Mg, some B.

The oil has been updated at least once since then (latest update 2014), but the numbers are consistent with what I’ve heard and read from Idemitsu.

Am I right to imagine that all of the above seems to imply a different formulation strategy vs. most oils? To my amateur eye, it seems to be part-way between a typical PCMO and a low-detergent race oil. The primary emphasis seems to be on AW/FM, with limited amounts of detergent/dispersant keeping ash low and reducing competition with the AW/FM; the latter point means they could use moderate levels of ZDDP, further reducing ash, but still retaining a very high level of AW performance.

I guess they could be using ashless detergents/dispersants, but I'm assuming that's unlikely at this oil's $8/qt price point, which already seems cheap for a PAO/ester oil. If that's a bad assumption, someone please correct me.

If I'm right -- which is a big IF, as I am not remotely an expert in the relevant field -- I bet this could be a killer option for short OCIs in many kinds of engine. Most other oils that promise high AW performance and have a lot of FM also have a bunch more detergent/dispersant, which may be useless or counterproductive for short OCIs. I wonder if this oil might beat them for AW performance. It'll certainly beat them on ash formation.

Thoughts? Corrections? Comments?

 

[ARCOgraphite]

The Idemistsu 5w30 Subaru WRX STI oil looks pretty good too. if you are looking for big moly.

Im not so sure about moly anymore.

 

[Lasthope05]

Why the need for a special oil? Don't most people with a rotary go with an external tank for the OMP or just delete it and run 2 stroke?

 

[HKPolice]

Racing oils = fewer detergents because they're expecting you to change the oil within 5K miles or after a few track days max.

Rotary engines naturally burn oil by design, this formulation will slowly kill your catalytic converter because of the high amount of ZDDP + Moly.
Then again, it's racing oil so they're probably expecting most users to run their cars catless.

Overall, not a very good formula for a daily driven RX8 but great for track cars.

 

[d00df00d]

Originally Posted By: ARCOgraphite
The Idemistsu 5w30 Subaru WRX STI oil looks pretty good too. if you are looking for big moly.

Originally Posted By: Lasthope05
Why the need for a special oil? Don't most people with a rotary go with an external tank for the OMP or just delete it and run 2 stroke?

Originally Posted By: HKPolice
not a very good formula for a daily driven RX8 but great for track cars.

Could go into these points, but don't want to make this yet another "what oil should I run" thread.


Originally Posted By: HKPolice
this formulation will slowly kill your catalytic converter because of the high amount of ZDDP + Moly.

Wasn't aware that molybdenum was a cat poison, and can't find any corroboration on that. Got a link, by chance?

AFAIK phosphorus is the main cat poison, and on that score this oil doesn't exceed the API SN limit. Zinc is on the high side, but there are ILSAC oils that come close.

 

[Kamele0N]

Rotary engines doesnt like fully syn oils anyway....or better its seals doesnt bear syn oils (result in hihger oil consumption when they degrade)

 

[JAG]

I agree with your assessment, d00df00d. The emphasis seems to be strong on AW, low friction coefficient in the less than hydrodynamic regimes, low coking, and high shear stability. The amount of detergent appears to be enough for a medium length OCI. The MSDS shows the large percentage of PAO at 60-70% and a 10-15% mineral oil mixture that down further is shown to consist of Group I (likely, part of the additive carrier) and Group III. Esters are not mentioned and they don’t need to be. PAO doesn’t need to be mentioned either but if I were making SDSs, I would show the things I’d be proud of the oil containing.
http://4imgs.com/1086/sds_10w30.pdf

The PDS shows viscosity at 100 C to be 11.19 cSt.
http://4imgs.com/1086/IRO_10W30.pdf
VI: 164
CCS: 4001 cP
Pour point: -45 C
Flash point: 260 C = 500 F (extremely high)

 

[Artem]

Originally Posted By: Kamele0N
Rotary engines doesnt like fully syn oils anyway....or better its seals doesnt bear syn oils (result in hihger oil consumption when they degrade)


Nonsense.

Both being say, SN spec, the only difference in synthetic oil is equal size molecules vs conventional's random size molecules. Better resistance to heat, better cold flow, etc are a bonus for synthetic oil.

If both are SN spec, I don't see how a synthetic will eat any seals vs a conventional OF THE SAME SPEC.

The real issue is that, since the synthetic oil is injected into the Apex seal, due to the oil's resistance to burning, there's a chance for increased carbon build up if all of it doesn't burn cleanly. That's the only concern with synthetic in a Rotary and supposedly cheap conventional oil burns cleaner (although I doubt it, for some reason)

Run an external tank for the OMP injection and synthetic oil is actually RECOMMENDED for increased wear protection and longer Rotary engine life. Lol.

 

[d00df00d]

Originally Posted By: JAG
I agree with your assessment, d00df00d. The emphasis seems to be strong on AW, low friction coefficient in the less than hydrodynamic regimes, low coking, and high shear stability. The amount of detergent appears to be enough for a medium length OCI. The MSDS shows the large percentage of PAO at 60-70% and a 10-15% mineral oil mixture that down further is shown to consist of Group I (likely, part of the additive carrier) and Group III. Esters are not mentioned and they don’t need to be. PAO doesn’t need to be mentioned either but if I were making SDSs, I would show the things I’d be proud of the oil containing.
http://4imgs.com/1086/sds_10w30.pdf

The PDS shows viscosity at 100 C to be 11.19 cSt.
http://4imgs.com/1086/IRO_10W30.pdf
VI: 164
CCS: 4001 cP
Pour point: -45 C
Flash point: 260 C = 500 F (extremely high)

Thanks, JAG.

Curious to hear more on the part I bolded. Could you say more about how you came to those conclusions? I think I have some idea but I want to hear your reasoning.

 

[JAG]

It has a considerable amount of ZDDP and a lot of molybdenum, so that puts a lot of emphasis on AW and friction modifiers. The moderate amount of detergent may enhance anti-wear further, relative to a larger amount of detergents, since detergents can negatively interact with and compete with anti-wear additives. The low coking and high shear stability statement was based on the product data sheet and I believe them about that. I’d try if I weren’t so happy with Amsoil SS. Just a thought: it would probably also be a great lawn mower oil.

 

[d00df00d]

Originally Posted By: JAG
It has a considerable amount of ZDDP and a lot of molybdenum, so that puts a lot of emphasis on AW and friction modifiers. The moderate amount of detergent may enhance anti-wear further, relative to a larger amount of detergents, since detergents can negatively interact with and compete with anti-wear additives. The low coking and high shear stability statement was based on the product data sheet and I believe them about that.

More or less what I figured. Thanks again.

Originally Posted By: JAG
Just a thought: it would probably also be a great lawn mower oil.

Interesting!

 

[weasley]

Thinking about this, one fundamental difference between a rotary and recip engine is where on the Stribeck curve they operate. In a recip engine we have very high loads in the cam-to-follower contact, tending towards mixed or even boundary conditions. Also at piston turn-around zones you also tend towards a reduced oil film, especially at TDC where it's hot and high pressure. In a rotary the rotor is continuously moving, albeit with varying relative speed between the rotor and housing. Of course there's no cam loading, but there is the primary gearing which adds a different, more EP kind of situation.

Thinking like this, it makes sense that a rotary oil should be different to a recip oil and aimed at differing lubrication regimes. That's not even thinking about the oil injection and combustion issue.