ayrton012

Maybe you are right, but I think the secret is in the oil temperature. If you use a thinner oil, than much more important to keep the oil level at the max. than with the thick oil. A lot of people only refill the oil when the lights come on. With a thicker oil is not as much dangerous as with the thinner oil.

Another truth is that you can keep lower the oil temperature with a thinner oil (at high rpms). So it is possible that you can get the same thickening with a xx-30, as the xx-40, if you dríve hard the engine.

BMonkey

*Removed*

firebirdude

iTrader: (3)

Correct me if I am wrong, but I believe the reason the damage was done in the first picture WAS due to inadequate oil film.... however the owner had an internal coolant leak which when mixed with oil would not allow proper protection. Thereby causing damage. It wasn't the owner using 5W-20 and over time proved inadequate causing damage.

I don't disagree with what's being said in this thread. I just think those pictures are being misrepresented.

StealthTL

iTrader: (1)

Agreed firebirdude - I don't see the link between 5W-20 being the standard spec oil on most US cars, and bearing failures. There just is no such data.

Don't you think that any increased wear rate, affecting millions of motors in all areas of the USA, would be fairly obvious?

These oils didn't exist in the 1990's - so any 'experiences' with thin oils before that is invalid.

BMonkey

*removed*

BMonkey

They hide their "proprietary" information relating to actual oil test results. I pasted up all of the ILSAC documents stating that they are making the changes in oil to improve fuel economy and improve emissions equipment life. Look at the dates of the GF-1,2,3 introductions, funny how these new oils came into "favor" along the same timeline. I showed that Ford, our parent company, offers a longer warranty on a turbocharged engine thats recommended to use 15W-40 vs. other vehicles using 5W-20 and 5W-30. If you want more evidence relating bearing wear to viscosity, go to the SAE and shell out some cash and read some tech papers, cause there's tons regarding bearing lubricity.

nycgps

iTrader: (1)

I've seen pictures of a Renesis rebuild from Japan, the *rebuild motor* was using 5w40. it was I think with 120km on the motor, the bearing has a slight wear, but not as bad as anything I've seen from the us motors. The reason for rebuilding is that they guy is adding a Trust(Greddy) turbo and want a complete rebuild with ceramic seals.

Auto manufactures will never publish any data, cuz they know what 5w20 is all about, yea they will tell people that *to maximize fuel economy*, thats all people care these days, unlike the old days of which people cared about the life of their car more than anything else.

if 5w20 is *as good as the other oil weight* as you said, then why did Mazda recommend 5w30 almost everywhere else just not the US market ? That should tell you something isnt it ?

firebirdude

iTrader: (3)

Re-read your post. You persuaded readers to believe that damage was caused by using low viscosity oil, when in fact it was a coolant leak. End of story. No reason to get hostile. I have been agreeing with this thread since the beginning. Keep up the good sleuth work.

BMonkey

I didnt make readers do anything.
What is coolant at least 50%? Water.
What is water? an extremely low viscosity fluid.
What happened to that bearing? Water and oil mixed and the bearing didn't maintain adequate oil film to provide lubrication.
Was water mentioned in my post as a theoretical lubricant? Yes.


And thanks for the compliment, I'm sorry I'm defensive but I'd like if the thread doesn't degrade into mind numbing debate.

firebirdude

iTrader: (3)

Ok. How about I edit the word to persuaded?

Where did you even mention the word coolant? You didn't. Where did you say this damage was caused by water mixing with oil? You didn't.

You said low viscosity leads to inadequate oil film.

*picture*

That was caused by inadequate oil film.

I'm off it. See you at the track...

BMonkey

added a description for the picture, just for you

ayrton012

1. ..As you wrote, there was coolant problem with that damaged bearing, so that's not related close to oil viscosity.
2. Higher flow means higher separate pressure between the parts, and better cooling. All of this three is working for better protection. With a thicker oil you waste a lot of flow, because the bypass valve will open too early.
You will see higher pressure with the thicker oil, but it will goes away at the bypass valve, the pressure won't make circulate more oil in the engine.
3. 10PSI/1000 rpm and more 10 PSI at every more 1000rpm (20psi/2000) is just enough to separate the parts.
I'm aware of using xxw-20 oil, but I think an xxw-30 oil has a good balance between pressure, flow,cooling, so there is good protection.

I heard that an Formula-1 team use straight 5 weight oil in their engine. Why?
High rpms engine's need higher flow, so there is high separate force between the parts, and high cooling ability.

I think a lot of Renesis bearing problem are because of the low oil level. And if the low oil level meets with a thin oil (xxw-20) many times, there will be problems.

BMonkey

Wow, everything I posted has been wrong... You've solved the entire issue of oil in rotary engines! All of those companies that produce high performance oils with high viscosity grades, listen up! Ayrton012 has done all your research for you and you should all produce low viscosity oils from now on. Apparently formula 1 is using them, and we all know that formula 1 engines usually run 200,000+miles between rebuilds.

Ok, I'm over it. On a more serious note, I'm not here to break everything down for people to the most simplistic levels possible. If you don't get that a motor oil and coolant are both fluids and both have a viscosity, one obviously lower than the other, but both flow over a surface in a similar manner forming a boundry layer just of varying thickness... then that's fine. You have psychological validation of your own intelligence now, you "corrected" me.


Ok, this time I'm really off it. Sorry for the disturbance.

bigireland

thanks for the info.. threads like this singlehandedly improve the site on the whole..

claus

you must be talking about really OLD SA22 (1st gen) and not FC's (2nd gen) or FD's (3rd gen) right?

nycgps

iTrader: (1)

ROFL !!!!!!! lol !!!!!!!!

WantedTwo

iTrader: (4)

Epic burn.

robrecht

Uh, sorry if I'm off base here, but aren't you both recommending xw-30 oil for the Renesis as is recommended in most other countries without CAFE legislation. The real question for me is posed by those who recommend 10w-40 or even 20w-50 for the Renesis. Whereas others still point out some benefits of lower viscosity oils at higher rpms. See, for example, some of Royal Purple's recommendations for High Performance Automotive Drag Racing:

Import Engines Naturally Aspirated < 7500 RPM XPR 5W20
Import Engines Naturally Aspirated > 7500 RPM XPR 0W10

Domestic Engines - Small Block
Naturally Aspirated < 7000 RPM XPR 5W30
Naturally Aspirated > 7000 RPM XPR 5W20, 0W10

I asked Royal Purple about using heavier 10w-40 or 20w-50 oil in the current Renesis rotary and they would not recommend it:

"The heavier oils will rob you of horsepower, increase operating temperatures, cause metal fatigue, and cause you to consume more fuel. Heavier oils will give you some extra protection, but at what cost? All of our oils will provide the same level of protection, regardless of the viscosity. We are more concerned with the proper viscosity for your application.

A heavy oil lets say is as big as a softball, but the clearances on the motor are designed for a baseball. You can make it fit, but what are you doing to the oil?

We will protect your rotary engine better, even with a lighter oil."

By the way, I'm no expert (hardly!), just trying to learn by listening to both sides of a discussion.

BMonkey

I don't think I've ever seen molecules that are the size of sporting goods....or an engine with clearances so tight that molecules of any weight oil wouldn't be able to slip in. I know what they're trying to say, but you gotta remember, asking a company directly is a very grain of salt sort of deal. Are they telling you that because it's true, or because they produce 3 times the amount of lower weight oils and want to sell them? As far as the higher rpm, lower viscosity for Drag Racing ... that's not an application where maximum bearing life and extended operation is considered. They are trying to give you maximum power and a few degrees lower oil temp. Check out some that are going to be used for extended periods at high heat.

Busch / Cup Super Speedway (e.g. Talladega) XPR 10W40, 20W50
Grand AM / SCCA XPR 5W30, 10W40, 20W50

Here's a motorcycle one, but a more direct comparison between short operation cycle and long operation cycle oil usage:

4-Cycle MX / SX XPR 5W20, 5W30

4-Cycle Enduro XPR 10W40

Given the flexing nature of the eccentric shaft under high loads, I think it's very important to maintain a thick oil film in the stationary gear bearings. This is difficult because the oil passes through the rotors before it gets to the bearings, carrying away the heat of the backside of the rotor face and rotor sides. Then to get to the stationary gears it comes out of the rotor gear passing over the side housing that’s carrying the heat from combustion too. So this oil has already absorbed a large portion of heat by the time it drains out through the side and gets to the stationary gear. Then in the stationary gear it has to provide lubrication to the bearings experiencing the highest loads. A difficult proposition indeed…

robrecht

Thanks for that clarification. But why not go further and recommend 10w-40 or 20w-50? Is it because of the increased heat?

BMonkey

Why don't I recommend higher than 10W-30? a few reasons:
1) Not everyone is out flooring their cars everyday, I'm sure alot of people don't even abide by running it to redline everyday. For those people, a high weight oil isn't going to see extreme temperatures like a turbo'd rx8 at the track might see. In that case, a 10W-30 viscosity grade will help ensure decently low temperature startability (the part where alot of wear occurs anyways) and good power/fuel economy retention. There's no point in providing unnecessary protection that's going to sap a little horsepower and a little fuel economy in an engine that's not driven roughly.

2) I did recommend that season be factored into oil changing as well however, so for the summer here in Texas I run 10W-40 and for the winter I use 5W-40. This is pretty dependant on your own area, which is why I showed you all the temperatures in the J300 to reference the kind of temps you see where you live. If you're up in Canada or something, you'd probably want a 0W or 5W oil in winter. Here in Texas it is not uncommon to have 7-8 months with temperatures regularly in the 100ºF range so it's easy to get away with a heavy weight oil.

3) This ties into point #1 but if you drive it like you stole it, run a heavier oil (than my base recommendation of 10W-30)

robrecht

Thanks, BMonkey

ayrton012

Thanks!

BMonkey

Bump

Mazmart

iTrader: (12)

BMonkey,

Are you going to Sevenstock? I'd love to meet you and chat.

Paul.