so since the oil companies are making less thicker viscosities of oil, had a discussion with a fellow rotary owner, and he has switched to rotella oil diesel brand. its a thicker oil plus has better burn off abilities due to it being made for diesel engines which burn oil like rotaries. what are your thoughts, i currently use castrol 20-50 for summer, and 10-30 for winter, plus premix.

 

Viscosity isn't necessarily related to the ability to protect the engine. Thinner oil is actually better as long as it doesn't break down. In my climate, I don't see any excessive wear even with Pennzoil 5W-20 conventional, changed every 3k miles/5k km. Of course, if you live in Texas and track your car on a regular basis, then XW-30 or XW-40 may be necessary. What's the climate in your area like?

As for brand, doesn't matter to me as long as it's reputable. Pennzoil is my go-to because it goes on sale often and I can get a 5qt/L jug for CAN$20.

https://540ratblog.wordpress.com/201...-test-ranking/

 

Do you have valve tappets or cam lobes that require high zinc for protection? My bet is no. So diesel isn't doing anything for you. It's still oil and it still does oil things, but provides no advantage.

I've been running LiquiMoly for the last 5-6 years and the used oil reports came back stellar every time.

 

Pennzoil 10W40 is what I have been running, for the 14,000 miles I have put on the car since I bought it last July...

I also started running it in my 3000, that used to only get Redline 20W50, I think now the 20W50 was too thick, because it seems to be happier on the 10W40..

I would like to run a little bit higher end oil, but I have a a few small oil leaks, and do alot of hard driving, so I find my self topping off the oil 1-2 times a week depending on how much I drive...

I will probably stock up on Redline but an appropriate weight again for both cars soon...

What about Premix? I prefer something easy to find or cheap to buy in bulk....

 

Mobil 1 0W40. Use a weight that is appropriate for your climate and change it frequently. Those things are far more important than brand.


Also, the additives in diesel oil tends to kill catalytic converters. Don't use it if you have one.

 

I'm running RedLine 5-30.

Diesel oil has to much, calcium bicarb and detergent which reduces it's lubricity. It is tough and has a good service interval. It does not have crazy amounts of ZDDP (1100ppm phosphorus) anymore because diesel trucks now have cats as well.

 

Castrol GTX 5-W-30

 

According to that, we should all be using Quaker State Ultimate Durability 0W20 with a $5 rebate from Wally World for a total of $15 per 5qts. Hmmm... I wonder how that would stand up in my Miata track car?


That sounds ludicrous, except that a lot of spec Miata racers use 20W oil and only fill it to the bottom of the dipstick. Of course, they probably change it before every race...

 

But like mentioned, protection level isn't necessarily related to the viscosity, and lower viscosity can offer some benefits. I have read that around 20% of cooling is done by the 2 oil coolers we(6-speed guys) have, and a thinner oil can help with cooling.

Of course, if I live in Texas, I probably wouldn't use 5W-20, either, but 20W-50 is just overkill in almost any condition. Just imagine all the cold wear you'd have...

If you are curious, you can just run a thinner oil, get a UOA and find out.

 

The oils wars have raged here for years, and there is no point in starting that up again. The conclusion is to use whatever makes you happy and change it frequently.


IMHO, where the RX-8 is concerned, 0W40 strikes the best compromise in hot climates like Texas--at least in the summer months, and especially if the car sees track time. Cold startup wear should be OK with the 0 cold viscosity rating, and the 40W improved viscosity stands up to shear for ~5K miles of mixed driving.


Getting back to Miata racers, they use the thinnest oil that will build pressure and as little of it as possible. They are looking for every last 1/8HP out of those 92HP engines, and they assume 1 rebuild per season. They also want to save weight and reduce foaming, which explains running it low. Oil coolers and catch cans are not allowed in the spec.



In my Miata, I run the same Mobil 1 0W40 that I run in my RX-8 with the addition of a 19 row oil cooler (200F thermostat) and a catch can. I run my level halfway between low and full on the dipstick (any more than that just ends up in the catch can). 40W is probably overkill, but I can't imagine it does any harm, and I don't care to replace my engine yearly, so...

 

I agree with the 40wt concept. There is a tremendous amount of shearing in the wankel engine. Any 0, 5 or 10,-40wt is good IMO. There are a few things that I like about the 0 weight ester oils and one I don't. The pros are they seem to have a bit more phosphorous and the M1 race oils are both 0 weight so there is obviously no issue with the performance of the 0 weight ester. The only negative is that it is not compatible with the other weights. All of the 5,10 & 15 weights can be mixed. Do not use 0-20 oils it appears they were developed for hybrids.

The oil coolers are more for keeping the oil temps in an acceptable range for the longevity of the oil. Especially if a mineral based lube is used. The oil is not as much of a factor for cooling primarily because the coolant is much more effective and also these engines have a very limited oil volume. Decreasing the oils temp will have little to no effect on the engines base temp. The heat transfer of oil is very low. If you want to decrease engines temp in a liquid cooled engine you should to do with the coolant.

 

The W in the front doesn't stand for weight, it stands for winter, which represents the cold viscosity. And to note, cold 5W-20 is actually still thicker than hot 20W-50. SAE oil rating is a bit weird that way.

And 0W-20 is not just for hybrids(which is actually rough on oil as well). Lots of NA and even some turbocharged family cars use them. I had my doubts over them, but they also give you the least amount of cold wear possible. And 0W-20 is still thinner than 0W-40 when cold.

Like Steve said, don't want to start another war here. Just use whatever that's appropriate for your climate and change often. Use UOA as necessary to figure out if your oil is indeed too thin.

 

I was just abbreviating weight with W. No war starting here. Hybrid engines typically have a lower load depending on the application, but in some cases they can run as the sole power source with a mechanical drive. Usually they are a supplemental power source or working as a power generation at a constant speed.

The 0-20 oils seem to have less EP. The M1 0-20 only has 650ppm of phosphors which is inadequate for performance applications. The 0-20 and 0-40 weight oil should have the same viscosity at room temp, but the 0 weight in this case refers to the type of ester not the finished product. The 0-40 has a CST viscosity at 40C of 73 and the 0-20 has a CST viscosity of 44.8.

 

I would challenge the notion that there is a tremendous amount of shearing. The bearing load is pretty well distributed and constant, there is no reciprocating movement and is supplied oil under pressure. The apex and side seals don't have a shearable oil film to begin with, so no shearing there.

The effects of shearing in a piston engine typically manifest at the up/down surfaces of rod bearings, various parts of the valve train that get rolled/smacked. None of that exists here.

It's a hot engine, but it's not a violent engine.

I'm starting to think that Mazda's 20 weight recommendation isn't at all crazy, because the thinner oil is more likely to be spread to larger area on the inside of the housing than a heavier one. Keep in mind it's constantly being supplied and consumed, so how far it can travel in X time under X force makes a difference.

 

The main source of shearing is from the gears. There is also some shearing in all of the boundary layer and hydro-dynamically lubricated components. I have spent over 8hrs reading posts on the lubrication of the wankel engine in this forum. It appears most seem to want to be educated about the lubricants but don't really understand the application. Usually lubrication is a compromise. In this case it is for several reasons. The wankel is just not as practical as a piston variety and a piston will soon be not as practical as electric.

 

I mean sure, but there aren't any reports of rotaries dying from gear wear, nor massive amounts of iron in used oil reports. Those gears don't see that much force, the eccentric shaft bearings take most of it. Otherwise the engine wouldn't work

 

I've sold lots of industrial oils, and read lots of uoa's. Many guys ran 15w40 in their Chevy 350 and got 500 k miles many times.
I'm sold on Mobil 1 0W40 as it's more like 0w35.
Mobil 0w30 isn't near as stout but Castrol 0 w30 probably is.

I can drive easy on my 07 Gt Auto with 18800 btu trans cooler, and water thermostat goes back into 177 degree nearly closed water flow.

That appears for the two oil coolers to be doing most of cooling work on days not hotter than 80 deg f.

Cooler intake and outlet is always 14 deg f difference.

 

So in order for there to be a shearing action there would have to be a component failure? Motorcycles are notoriously hard on oil because the engine shares the crank case oil with the transmission.

I wonder if a higher viscosity oil is good idea because it may decrease bottom end wear and/or have a stabilizing effect on the rotor. There is a fair amount of inertia on the rotor and I believe some of the rotor/housing and seal issues could be initiated, accelerated or caused from bottom end issues.

 

The ratio of cooling between the coolant and the oil is drastically different. The heat transfer rate, cooler surface area and volume dictate which has more of a contribution. It could be 10:1. I'm not a firm believer in spitting hairs to find the most ideal oil. If it has enough viscosity at the end of it's service life it is most likely ok. There are areas/times that the oil film is compromised and then the system relies on the EP to prevent welding. I would try to use a product that has at least a 1000ppm of phosphorous and more if there is no cat.

 

10~20% of cooling effect is still not negligible, though.

And yeah, changing oil often is the key. Really doesn't help that the whole lubrication system holds 7+ litres/quarts of oil and we can only get 4 out each change.

As for the phosphorous comment, I don't think there is a product out there with that much phosphorus. The Pennzoil yellow bottle 5W-20 conventional has close to 800 ppm of phosphorus and that's close to the top end. You can find out at pqiamerica.com. The only way is to add some kind of additive to your oil.

 

In my first post there is an attachment with the phosphorous levels of the different M1 oils. There are two 0-40 products one with 900ppm and the other with 1kppm. This is part of the reason why I like this particular product.

 

Then use that if that's what you are looking for.

Will probably do another UOA next oil change since I now AutoX monthly and still drive pretty hard.

 

What do you consider the bottom end in a rotary?

Shearing is parting of the oil film that which allows metal to contact metal and produce wear. Since we don't see excessively worn gears or iron in the oil, it seems safe to say there isn't a significant amount of metal to metal contact, thus the oiling for those components is adequate. Even with the Mazda-recommended 20 weight.

So what I'm saying is, bearings and gears live longer than rotor seals in the status quo, therefore we should prioritize lubrication of the rotor seals to get some kind of lifetime improvement.

Totally agreed (plus other UOA factors)

 

The bottom end reference is not off just because the rotor circumscribes the eccentric shaft and the engine is horizontal. It does have an operating direction. There is a stroke, reciprocating motion, linear component of the motion vector, compression and a combustion direction. Just like any other two stroke.

Shearing is when the molecular structure is cut and the result changes the mechanical properties of the polymer. Your second to last statement is the common logic. How have we progressed because of it?

I believe Mazda has more experience then anyone or nearly anyone in the world on this topic but the engineering data is trade secret. I'm sure the compromises are really the limiting factor for longevity

 

As to the bottom end of stationary gears, I've seen the massive wear there on th bearing in some teardowns.

That seems to be where thin just isn't good.

I don't use much oil, so my Mobil 2T premix is most of seal lube.

UOA coming in a few months.