I'm trying to figure out what to get for my engine. I know that there are thousands upon thousands of threads regarding oil, but all of them have different answers. I have twin oil coolers and a big single aftermarket turbo (That's how I got the car). The previous owner used 10w40 from ELF, and I want to switch to something designed for the rotary engine, like Idemitsu. I've seen people say that you can use 10w30 if you have oil coolers because you won't have a problem with heat.. and even suggest that your engine will last longer if you use 10w30, and other people say that 20w50 is for more "spirited" driving and even racing even WITH oil coolers. I have plenty of oil pressure at idle, (2.2 - 2.5 bar, 31 - 36 psi) with my current oil, and I haven't seen or smelt any oil dilution. I am afraid that 20w50 will be TOO THICK and I don't want to break anything. What should I use?

 

10w-30 is what the manual recommends. One of the main reasons for the 20w-50 recommendation floating around is due to fuel dilution, thinning the oil.

If the motor is newer with good tight clearances, use 10w-30. If it is older with looser clearances, perhaps split the difference with a 10w-40. The number one thing is to simply change it often.

 

The engine was recently rebuilt. Idk about bearings and such. What would the safest option be even if it means changing the oil every 1000 miles

 

Smell the dip stick for fuel every 1k miles. Change every 2-3k miles or once a year whichever comes first.

 

It does smell a bit like fuel.. It is a bit black (still see through though) and it's got 1000 km on it. The engine being rebuilt, and the mechanic recommended 20w50 VR1 from valvoline (which is way more affordable and common for me), I tend to go with the mechanics choice, instead of paying for fancy rotary specific oil... Being a new owner I am scared of anything because this thing means a lot to me. Is the oil the mechanic recommended good (does it have a good reputation? I've heard mixed things about valvoline).

 

I use 20W50 VR1. 65k miles on stock motor. Great oil, easy to get.

 

The issue is i'm not stock. I don't really know what to look for when smelling the dipstick because my friend with a RX8 has the same smell.

 

Unless you're in a very cold climate, I will always suggest 50wt. There is no crank to worry about slapping against thick oil and windage shenanigans such as with a piston engine, and oil pressure at temperature in a rotary is paramount.

 

now that these cars are older, i feel like we as a community are going more by condition of the oil than any kind of mileage/time
so if the oil is dark and smells like gasoline, its probably time to change it.

the nice thing about these engines is that they aren't very picky about what kind of oil you use, although they do like fresh oil

 

Thanks. I've settled for 20w50 idemitsu

 

This is a Blackstone Labs oil analysis report for Idemitsu 10w30 after only 2000 miles of street driving in a 60k+ miles RX-8. Notice the viscosity is already below range.
This is an NA Renesis, turbo blow-by and fuel dilution is usually worse. This supports the mindset of using 20W50 in rotaries except for extremely cold weather. I know it's a single point data set but it correlates with others.

 

I've had no problems running 20w50 in near-freezing temperatures. With air temperature showing about 40 degrees F, ECU datalogs show the oil temperature gets up to 90 degF after running for 3 minutes, and 140 degF after 10 minutes. On a warmer day with air temperature about 65 degF, oil temperature gets up to 90F after running about 2 minutes, and 140 degF after about 8 minutes. I agree the oil gets smelling like fuel even without lots of miles, it seems like a good reason to change it often. I really should try the oil analysis tests sometime.

 

You shouldn’t be running hard or into boost until warmed up anyway.

 

Correct, I didn't specify but those datalogs I found are both sitting and idling while the car warms up so it was a pretty consistent set of conditions aside from the temperature.

 

I don't drive it at all until it's warmed up 😂

 

Then why this thread? Why are you so conflicted on viscosity?
You know your climate and don’t boost cold, and you’re willing to pay premium for (supposedly) superior oil.

 

I just said that I'm new and I've heard alot of mixed reviews about oil viscocity. I don't want to break anything, that's all.

 

The best warmup is driving gently until you see oil pressure start to reduce a bit and water temp is at 180F or higher. Idling until warm creates more oil dilution with fuel and/or combustion water than gentle driving warmup.

 

You could get really crazy and mix the 2. All 10w30 and throw in one 20w50 to thicken it up! Make your own 15w40! Or whatever.
Yes, it is ok. Yes, both manufacturers Idemitsu and Royal Purple said there is 100% no issue with mixing them...

 

I see! Thanks! As I said, I've settled on 20w50 during summer, and maybe mix the both during winter.

 

Unfortunately I can't do that since my drive from home to the freeway is like 3 mins . The cat doesn't warm up fast enough in those 3 mins before I hop on the highway.

 

Good YouTube channel that explains how boost and other factors effect oil:

 

I appreciate this video. What a glorious sound to listen to as I have my morning cup of coffee... Hmmmmm,.....Maybe I should run 20w50 with a bottle of 10w30 in it instead of the other way around lol.... this video does make me think a bit. Just kidding, but Thanks for the info.

 

it’s not that there are millions and millions of oil threads, but there are millions of millions of not informed people excessively fussing over splitting hairs into indiscernible pieces.
.

 

Until the "pros" such as yourself come together with one or two simple answers there will always be misguided answers to questions.. Or , what one would think is wrong or right.
Water injection or water/meth injection brings up a whole new challenge in lubrication. How many housings have been possibly trashed for lack of lube. The meth may very well be washing off your lube. Hell, how much does water affect the omp or premix lube? Does a thicker oil help prevent that? 10w30 vs 20w50 "dripping down" waiting to be distributed along the housing. Obviously, an oil resistant to meth may be a good answer? What about the water? The whole thing happens pretty quick. I came up with my own conclusions, which is all anyone can do. We can look at the guys who take the time to share info when they break engines down and share what may have caused wear. This is really the only way to learn. Even then, they may have an ignition that is a bit to hot, or whatever that they believe is totally fine, because " I've been doing this for the past 30 years" ... I have people (pros on here) tell me I am wrong for mixing viscosity when the actually little scientist guys at the actual oil companies tell me there is nothing wrong with that at all. Speaking of RP and Idemitsu.
I get it. I understand why these threads pop up. I can appreciate anyone that wants to do wlthe right thing with the car. They are representing the rotary world, so we should still try to help.
Maybe there will be some new Intel one day we can all look upon and benefit from.