Minimum HTHS for Rotary engine in RX8?

[unDummy]

I could care less what Mazda says or recommends. That synthetic argument has been going on for 2 decades. Mazda is lying!

I still haven't seen a failure or issue caused by using synthetic oil in a rotary engine. My 13b's have always run synthetic and I still haven't broken one yet, and I've try!

Every rotary engine failure that I've seen was caused by Mazda or by a clueless owner that trusted Mazda!

 

[typ901]

Well it has been years since I had my FC, but I ran the [censored] out of that car. 130k miles of hard driving. I put in Pennzoil and Castrol 10w-30, whatever I could get by the case. 1 Quart/1k miles was my norm. Mazda must have cut back the amount of oil injected-mine ran great.

 

[quint]

Mazda made a "no synthetics" rule due to one specific brand of synthetic oil causing the apex seals to chatter rather than smoothly slide, and since they didnt want to specifically not recommend one brand of oil over another, and spend a lot of money testing which ones would work and which ones wouldnt, they made a blanket statement for no synthetics. I got that information from a (who I trust) Mazda source. Go onto the Rx7/Rx8 forums and you will see people everywhere using synthetics with no problems.

I loved all of my Rx7's and if it werent for a horrifically short lifespan of my last turbo which scared the wife off the rotary scene for the time being, I'd still be driving one. And since my very old neighbor has an absolutely *mint* FB in his garage which he almost never drives, I am merely sitting and waiting patiently for him to give in to my incessant requests to sell it to me when the wife aint looking.....

 

[zoomzoom]

Originally Posted By: rg200amp
Originally Posted By: unDummy
Any current oil spec will work fine.

It extremely important to do frequent oil changes. Never go over 3k/3mo and it'll last a long time.
Also, its critical to top off oil at EVERY fuel fill up.

Make sure you have all recalls/TSBs addressed.

Run a little 2-stroke or UCL premix in the fuel always since 'emissions tuning' doesn't inject enough motor oil for seal lubrication.

Research oiling improvements in the form of aftermarket coolers, thermal-pellet mod, upgraded oil pump, increased oil PSI, aftermarket oil pan, windage/aeration control, and the 2-stroke oil metering pump adapter.

With the movement toward some low/mid SAPS oils, I'd probably go to Synpower MST/HST or the Mobil1 ESP oils, or equivalent. Anything to reduce crud buildup, will help a neglected engine.

Run a bottle of quality FI cleaner at every OCI. Gumout Regane, Techron Concentration, 3m, BG44k, Amsoil PI, Redline SI1, FP60, Neutra... are some that I'll recommend.

Get a quality oil temp gauge since your oil temp should NEVER go over 200F. Rotary engine oil is 'cold' compared to 'piston' engines.

Never shut off a cold engine(no swapping parking spots without a 10 minute ride). If you must, rev to 4k just before shutting her off. The flywheel momentum will help 'vent' the engine to prevent flooding restart issues.

Research your VIN at the dealer. You probably already have a new engine or 2, since most rotary owners were/are clueless.


+1 on everything!!!

Sorry to say it. But I dumped my Rx8 AS SOON AS I COULD once I was out of the red in my autoloan.

The things are fun to drive in the twisties, but are BAD as daily drivers.

They are not that fast. They get bad MPG. Lot's of issues with engines. Man, I don't miss that thing. I was getting better MPG in my 6.8L V10 F250 than the Rx8.

Change the oil every 3000k. When you change the oil, a lot of the old oil stays in the oil coolers and lines. So a oil change only gets you some new oil.

Did I say that I DO not miss that car!!!!

lol


you are slowly making your way to Toyota, which is boring but will make you worry free..I don't mind a bit more maintenance for the all fun I get out of it on the track and street.

 

[rslifkin]

AFAIK, the "no synthetics" thing is only for US RX-8s. I think it's partly for emissions reasons, as well as what Quint said.

 

[unDummy]

For emissions, they simply leaned out the oil injection causing engine failure.

Chatter is usually caused by loss of lubrication, or defective seals/springs/housings/build quality.

Idemitsu sells rotary lubes. Guess which Mazda rotary powered race vehicles had Idemitsu sponsorship?

I'm also at a loss why those superior engineers at Mazda can't give the oil injection systems its own sump and some JASO/NMMA certified injection lubricant. Are consumers that incompetent to tell the oil fills apart? They think so!

My Mazda source, over 20 years ago, stated that certain big oil companies promised but pulled race car and track sponsorship, and had NOTHING to do with lubricants ability. Stick it to the market leaders!

They also didn't see the need to burden the consumer with the synthetic expense. Oil temps tend to be overly well controlled in a rotary.

 

[kemo]

I read a lot of second hand gossip here on why NOT to use synthetic oil in a rotary Mazda...

Here is what I KNOW:

Quote:
According to Mazda Corporation Engineering bulletin
#06010010 dated 10/27/2006, injecting synthetic engine oil
into the combustion chamber of the RENESIS engine may
lead to carbon buildup that adversely affects engine performance.
Mazda conducted a case study with the use of synthetic
engine oil in the rotary engine, finding it caused a large
amount of viscous carbon buildup on the side housing. Mazda
did not conclude that this carbon buildup contributed to
adverse engine performance, but did state that if carbon
buildup adheres near the spark plug hole, or to the seals in the
combustion chamber, it may lead to adverse effects such as
engine misfire or knocking.

 

[CATERHAM]

Originally Posted By: d00df00d
You don't need a min. HTHS of 2.9 in ALL piston engines. It depends on the design and the type of service.

And ultimately it depends on oil temperature.

HTHS viscosity is more than anything else best thought of as simply an accurate measure of an oil's viscosity, and in that regard it supersedes the KV100 viscosity spec'.
If you keep the oil temp's low you can run very light (low HTHS vis') oil, the engine doesn't know the difference. For example that's why you can run a 5wt (HTHS 1.7cP) qualifying oil in a 800 hp Nascar engine for a few laps, the oil temp's never (and must not) exceed 180F.

In zoomzoom's RX-8 the spec' oil is a 30wt with a typical HTHS of 3.1cP or so. To minimize wear, at the very least he doesn't need to run an oil any heavier than that. But if fuel dilution is an issue with the engine as unDummy suggests, thereby necessitating frequent oil changes, the oil's viscosity loss (HTHS vis' loss) could be significate by the end of a normal OCI and track use may or may not exacerbate that.
Running a grade heavier oil than spec', like RL 5W-30 or T6 5W-40 would only seem to be beneficial to counter anticipated fuel dilution.

What I would suggest is to install an oil pressure gauge; an oil temp gauge as unDummy suggested would be good too. An OP gauge should be mandatory fitment to any car that's tracked. One advantage of an OP gauge is that it's like having an on board viscometer. Get the minimum OP spec's for the engine and see how they compare to the heavy oil you're running now. You may want to try a run of some spec' 30wt oil for reference to the minimum oil spec's. With fresh spec' 3.1 cP oil the OP will of course be higher than the min' OP spec's but you will know if the OP drops as mileage builds up and if the oil is thinning either due to shear or fuel dilution. You will also know if it tests the min' OP spec's when the oil is as hot as it ever gets.

That's your safety margin and since HTHS vis' correlates precisely with OP it's also how you fine tune your oil viscosity selection to your engine and how you use it.

 

[unDummy]

Originally Posted By: kemo
I read a lot of second hand gossip here on why NOT to use synthetic oil in a rotary Mazda...

Here is what I KNOW:

Quote:
According to Mazda Corporation Engineering bulletin
#06010010 dated 10/27/2006, injecting synthetic engine oil
into the combustion chamber of the RENESIS engine may
lead to carbon buildup that adversely affects engine performance.
Mazda conducted a case study with the use of synthetic
engine oil in the rotary engine, finding it caused a large
amount of viscous carbon buildup on the side housing. Mazda
did not conclude that this carbon buildup contributed to
adverse engine performance, but did state that if carbon
buildup adheres near the spark plug hole, or to the seals in thecombustion chamber, it may lead to adverse effects such as
engine misfire or knocking.


Meaningless. What oil? Lets go Mazda. You slam ALL but don't prove it by testing ALL. I'll give Mazda a hint because they seem to not remember. You can't run rotary pig rich to keep the emissions(NOx) happy and expect the engine to last. Saving face by pointing the finger in other directions is WEAK but other automakers do the same.

 

[NateDN10]

Originally Posted By: unDummy
Meaningless. What oil? Lets go Mazda. You slam ALL but don't prove it by testing ALL. I'll give Mazda a hint because they seem to not remember. You can't run rotary pig rich to keep the emissions(NOx) happy and expect the engine to last. Saving face by pointing the finger in other directions is WEAK but other automakers do the same.

Running rich reduces NOx, but increases HC and CO, so that's not the problem. That's why in closed loop, the ECU constantly goes back and forth between slightly rich and slightly lean. You need both for emissions.

Maybe they're just not injecting enough oil to keep the seals happy (also for emissions reasons).

 

[SteveSRT8]

Everybody runs pig rich out of closed loop.

The whole thing is apex seal lube as undummy says. We had 3 different rotaries in the 70's, the RX-4 sticks in my mind as one of the BEST engines ever. With minor mods mine ran 10,000 revs without a whimper for years, never missed a beat.

If I ever got another I'd be going for the separate injection tank with two stroke oil in it!

 

[ARCOgraphite]

Originally Posted By: unDummy
Originally Posted By: kemo
I read a lot of second hand gossip here on why NOT to use synthetic oil in a rotary Mazda...

Here is what I KNOW:

Quote:
According to Mazda Corporation Engineering bulletin
#06010010 dated 10/27/2006, injecting synthetic engine oil
into the combustion chamber of the RENESIS engine may
lead to carbon buildup that adversely affects engine performance.
Mazda conducted a case study with the use of synthetic
engine oil in the rotary engine, finding it caused a large
amount of viscous carbon buildup on the side housing. Mazda
did not conclude that this carbon buildup contributed to
adverse engine performance, but did state that if carbon
buildup adheres near the spark plug hole, or to the seals in thecombustion chamber, it may lead to adverse effects such as
engine misfire or knocking.


Meaningless. What oil? Lets go Mazda. You slam ALL but don't prove it by testing ALL. I'll give Mazda a hint because they seem to not remember. You can't run rotary pig rich to keep the emissions(NOx) happy and expect the engine to last. Saving face by pointing the finger in other directions is WEAK but other automakers do the same.
Sounds like you need to run TCW3 in this thing. OTW not enough difference in the base oil AFA flash point or Ignitability or clean burning. The biggest differential would be that the detergent and AW add pack was ~1/3 again more fortified over a comparible group ii oil. Some formualtion may be suboptimal on certain engines. Subaru has been constantly telling owners NOT TO RUN synthetic in their NA engines - and I was told the same when I bought our 09 - but I have not seen a TSB published. Same with VW years ago in the late 80s and early 90s recommending AGAINST synthetic use in the OM unless required by extreme climate.

 

[quint]

Originally Posted By: unDummy
For emissions, they simply leaned out the oil injection causing engine failure.

Pretty much.

Originally Posted By: unDummy
I'm also at a loss why those superior engineers at Mazda can't give the oil injection systems its own sump and some JASO/NMMA certified injection lubricant. Are consumers that incompetent to tell the oil fills apart? They think so!

My understanding is the engineers wanted to do just that for the Rx7, to cure some of the ills that plagued the Rx2/3/4/5 etc and the marketing department said no way. I remember reading this a long time ago.

 

[Spazdog]

I wonder why it just became an issue in 2006. It's got to be a RENESIS issue.

I ran Castrol Syntec 5W50 in my 12A powered '84 RX-7.(that was the only weight Western Auto carried at the time) There was never an issue. On anything. The car ran flawlessly.(although I did only put about 20K mi before it was stolen and stripped.)

 

[vinu_neuro]

Considering the low temps I'd just run a good dino like GTX and use a small amount of 2-stroke oil in the fuel each time you fill up. I know a lot of RX-8 owners have adopted this practice (although many still use synthetic).

 

[zoomzoom]

Originally Posted By: vinu_neuro
Considering the low temps I'd just run a good dino like GTX and use a small amount of 2-stroke oil in the fuel each time you fill up. I know a lot of RX-8 owners have adopted this practice (although many still use synthetic).


hm I wonder if these new GF5 dino oils are good idea in this engine?

How are they showing in the UOA's?