Good technical discussion about Engine Oils
 

This is a great thread to give you a general understanding of motor oil properties. The needs of a rotary engine dictate that this info has to be taken and considered slightly differently, but the general principles are the same.

I found the stuff about oil pressure as it relates to oil weight particularly interesting...

http://ferrarichat.com/forum/showthread.php?t=136052

I like what I've read so far. I'll need some time to get into this article properly.

Paul.

I notice that Haas does not discuss oil temps below 75F. Any coincidence to the idea that API uses 75F ambient for their viscosity paradigm? The cool thing about Haas's "article" is that he attempts to explain the other half of the issue, the one that the OEMs typically leave out of the equation because they assume to know the typical engine operating temperature for the typical driver/owner. Haas's article certainly gives us something to ponder.........

Wow, now my whole line of thinking has changed. How about installing an oil warmer? haha.

I guess I owe all you synthetic addicts an apology (NYCGPS).

While Synthetics may not burn as good as dino, I am convinced the added benefits at cold start up carry way more weight in terms of longevity as long as you premix as well. I guess I'll be running 0W-30 synthetic and premix.

Wow, no one has chimed in yet? So i was thinking what would the difference be in terms of operating temperature of Synthetic 0W-30 and 0W-40?

This is old news.

nah, dont say that. we all just want the best for our love (not you women ! LOL!)

Synthetic flows way better than mineral at start ups.

put it to simple terms, at operating temperature, the lower the oil weight, the higher chance of "metal to metal" contact will occur.

Also, when we rev the crap outa our engine, if the engine oil is not "strong" enough, the metal might just "touch" each other.

anybody notice that some oil company will label their "heavier" weight product to "High performance, high RPM, etc" blend or something. Quakers State Advance Q, for example.

So yeah, heavier oil = better for higher rpm engines.





BTW ---- thats a repost of a repost of a repost :)

Think i'll go to a 0w30 synthetic after reading that . Currently using 5w40 synth

Anyone out there with an oil pressure guage fitted like to tell us what they get with various grade oils at what rpms ....?

If this is old news then why do so many recommend heavier oils when the 0W seems to be fine in normal temperature ranges? Synthetic vs. Dino aside, most of what I have read on this site points towards running 15W oils. It is interesting to read all this and see the differing opinions. I have emailed Dr. Haas and asked him to comment on Rotaries specifically. I will definitely be getting the RB guage pod soon.

Yeah I didn't want people reading something and immediately jumping over to 0-weight oil.....just food for thought.

THIS however, I am really interested in. Does anyone with a real oil-pressure gauge have any data on this? Also this might explain part of why mazda only put a binary "dummy" gauge in for our oil pressure: perhaps with the very thin oil they recommend, the pressure readout would vary so much as RPMS and temperatures changed, and confuse a lot of people?

very good information here
thanks for posting this

Not more on OILs... :) a repost of a reeeepost of a reeeeepost ;)

But yeah, just think that Mazda USA still recommends for the RX-8 a 5W20 "thins' down to after 1000 miles, again I said this a million years ago when engines were first dieing during that US summer.

Probably OK for Winter, but 'Water' in Summer.

Agree with Nycgps thicker the better.

Oh you guys are killing me! I have been looking into this a lot over the past 6 months with everything from engine oil, transmission oil and even 2 cycle oil for those of us using the sohn adapter.

This isn't exactly true.

The reason people have suggested the heavier weight oils is the myth that we have some kind of special circumstance that warrants these heavier weights. The fact is we simply don't.

I'm even prepared to argue that Mazda's suggestion of a 5w-20 is actually correct. I admit that I was part of the group that suggested using heavier weight oils (I even used 20w-50 for a time) but I have come to the belief that 20 weight or perhaps a 30 weight oil is the best solution for our engines.

The article might be a repost but how many of you took the time to read ALL of it? I bet not many.

Dr. Haas's argument and method of explaining oil changes your perception of how you think about your driving habits and the oil you choose. People comment about how a 5w-20 is "too thin" when they have a complete misunderstanding of how oil works.

Frankly, there's a huge connection to the misconception that boost = airflow when it's actually resistance to airflow. Pressure, in the case of oil, is resistance to flow as well.

Finally, when you examine your oil choice you don't think of oil as "thinning" as it gets hot but "thickening" as it gets colder. The most amount of engine wear is going to occur when the motor is cold, not warm. When you start your car cold the thickness is going to be much higher and thus so is the pressure.

Your oil will flow much more at 30psi than it will at 70psi. The problem with heavier weight oils is the pressure increase forces open the bypass valve. This allows oil to bypass our oil filter and go straight into the motor. Not only does this mean the oil isn't filtered but it could even wash deposits in the filter back into the motor.

It's a balance. You want to have an oil that is as thin as possible at startup but has proper thickness at operating temperature to provide enough pressure to move it but not so much pressure it's not flowing enough.

High RPM motors need thinner oils. It's flow that lubricates a motor, not oil on the surface. If you don't have oil flowing due to high viscosity conditions then it's not protecting your motor. It's as simple as that.

What needs to happen is people need to be really honest with themselves about how they use their car. Unless you're in a racing situation which creates high oil temps (usually sustained temps above 225 degrees) then using "race" oils or even heavier grade oils isn't necessary.

As a community we have long held that 5w-20 was too thin for the RX8. I think much of the truth is the quality of oil and the oil change interval that is responsible for engine damage and not the weight of the oil itself.

Edit: There's also the unaddressed notion of OMP injection amounts which no doubt were not enough to keep the engine lubricated. As an example, the lowest OMP injection amount on my map is 13/60. The stock map is set to 3!

I've seen plenty of RX8 owners going 5,000 to 7,000+ miles between changes or not filling their oil until the light turns on. As Haas points out, as oil ages it gets thicker not thinner (in the case of mineral oils).

Synthetics (true synthetics) hold their viscosity for the majority of it's life. The additive packages are what break down. This means you can go longer between oil changes.

The other problem is the habit of jumping into your car, not letting it warm up and then jamming on the gas. When you need lubrication the most you're not getting it.

There's a whole other side to this when examining the benefits/drawbacks of various base oils and additive packages. However, I think the weight of the oil is the most critical thing.

I'll admit that I just placed an order for some 0w-20 that I will use as my daily driving oil. I'm hoping to get a UOA done on it in about 5,000 miles or so and see how it's holding up.

Again, you guys are thinking about this from the perspective that the oil "thins" when you need to focus on the fact that it thickens as it gets cool.

At startup there's very little engine load, very little RPM activity and therefore the oil doesn't need to be thick because there's little need to protect the motor. The fact remains that your engine operating temperatures are going to be almost the same in winter and in summer. With a proper oil cooling system your oil temps should be approx 180 degrees in winter and maybe 200 to 210 degrees in the summer. The viscosity of your 5w-20 isn't going to change much with 30 degrees difference.

Haas goes with a rule that you need 10 PSI for every 1,000 RPM's and uses Ferreri's example of 75 psi @ 6,000 RPMs. This is easily achieved with even the 0w-30 Mobile 1 I'm running. I see approx 30 psi @ idle and 70 PSI by about 2,500 to 3,000 RPMs. I am sure your 5w-20 is more than capable.

The key is the more flow you have the more cooling your oil system can provide and the more lubrication it brings. Oil on the surface of metal doesn't lubricate, flow does.

If that's the case then why isn't everyone running SAE 90 weight oil in their motors?

"At startup there's very little engine load, very little RPM activity and therefore the oil doesn't need to be thick because there's little need to protect the motor"

There's more need to protect the motor, because there's only the oil film left clinging to the surfaces and no flow.
The thinner it is whilst cold, the more fllow you get = faster protection to the moving parts.

But yes, too thick is as bad, if not worse, than too thin, even with flat out rally stages and high oil temperatures (average around 120*c at full slog on the uphill sections), a 0w-30 fully synth. will easily hold 90psi at anything above 6000rpm - we'll go thinner once we've used this barrel of oil up (ain't sponsorship great :D )

Yes Phillip you're correct. I think where I was going with that statement is addressing the notion that a thinner oil at startup due to temperature increases is a bad thing. In fact, it's the exact opposite as you pointed out.

I think that a 0w-30 for race applications would be a good idea. The fact that you would have sustained higher operating temperatures would ensure your cSt is where you need it to be. However, for daily driving situations or a spirited drive I imagine a 20wt will be just fine.

Again, much of the myths surrounding engine oil for the RX8 has been the thought that we all drive our cars super hard and that means we need a heavier weight oil to protect the motor. The fact is that we all drive our cars the majority of the time within the limits they are designed for and thus a standard oil is fine.

There's also the difference between "Race" oils and "street" oils which is a topic that has long been addressed by other members of BHR in that we usually equate "race" with better and "street" with average.

Obviously there are extremes in both cases. Haas points out that while a straight 10 weight oil would be as close to ideal at startup as you could get, the cSt would be around 3 at 210 degrees and thus unable to provide the necessary lubrication the car would need.

Edit:

The real question would be what kinematic viscosity is optimal for the RENESIS motor? If we use Haas's stance that your average engine needs approx 10 cSt at operating temperature then naturally the best cSt at startup would be 10 as well. As he points out, there isn't an oil made on the market that can give you the same viscosity at startup as it does at operating temperature.

Let's use Eneos as an example since this is what I have been looking into....

I had planned on using Eneos's 0w-50 oils cause I thought I needed a 50 weight oil in my RX8. Now, due to the age of the motor (80,000+ miles) I might very well need a slightly heavier oil than 0w-20 but that's a different story.


Quality grade RG/API SM
SAE viscosity grade 0W-50
Appearance Orange
Density (15°C), g/cm3 0.847
Flash point (COC), °C 232
Kinematic viscosity (40°C), mm2/s 104
(100°C), mm2/s 18.0
Viscosity index 192
Pour point, °C –45.0
TAN, mgKOH/g 2.3
TBN (HCl), mgKOH/g 6.4
Color (ASTM) L3.0

Now compare this to their 0w-20


Quality grade API SM
SAE viscosity grade 0W-20
Appearance Orange
Density (15°C), g/cm3 0.854
Flash point (COC), °C 230
Kinematic viscosity
(40°C), mm2/s 41.5
(100°C), mm2/s 8.5
Viscosity index 199
Pour point, °C –45.0
TAN, mgKOH/g 2.4
TBN (HCl), mgKOH/g 5.1
Color (ASTM) L3.5

You can see the viscosity at 40 degrees centigrade is MUCH higher with the 0w-50 than the 0w-20. While both oils share the same pour point, clearly one is thicker at startup than the other. The 0w-50 is going to protect less at startup than the 0w-20.

Again, I'm still really learning about all this as my beliefs about engine oil seem to be completly out of phase with what I previously thought. I'm interested in any input anyone has regarding this information.

Hello there... I have an RX-8 and I bought it one and a half year ago, it has 47000 km and I have problem with my check engine light, it stays on all the time. I also found some white foam to the bottom of the engine oil, and when I switch on my car a white smoke comes out from the exhaust, can anybody help and explain to me what is happening??

I really go the extra mile to not use the "search noob!" statement but...

http://lmgtfy.com/?q=RX8+oil+dipstick+foam

That should take care of you.

Quote - "There is little advantage to a thicker based oil as a 20W-50 at very high temperatures"

Directly quoted from the chemist's article. The only benefit is the fact of it being synthetic, and I'm concluding that 5/10-20/30 is the way to go, synthetic. The 20w is worst at what the whole point of his article is; trying to get people to realize it's the start up that does the worst damage, not the operating temperatures or peak. Which is why 20w-50 in his eyes would be a poor choice. Of course this is if you agree with the author's findings.

Quote - "There is a huge advantage of using the thinner, 10W-30 at startup where 90 percent of the engine wear occurs. At 75 F the thicker oil has a viscosity in the range of 250 cS while the thinner oil has a viscosity of 100 cS. The thicker stuff is 150 cS thicker. This is a very big difference. I am using the 20W-50 as my thicker oil example here."

And from what I grasp reading other threads about oil, there were only 2 concerns revolving around synthetic but feel free to correct me otherwise. These were believed to "eat" away apex seals on the first released '04/'05 cars or at least contribute to lowering their life expectancy (can someone confirm this?) and that it goes outside of the manual's recommendations. If I recall they've fixed the apex seal material (again can someone confirm this?) and the manual only recommends so they have no basis for not covering your engine if you use a different weight based oil or synthetic.

Quote - "You do not need to use the exact oil type and brand that your car manual tells you to use. Oils are pretty general. They are not that different. Ferrari is married to Shell. If you call them up and ask to use Valvoline instead they will tell you that they have not tested that brand in their cars. They only tested the engine with Shell oils. They cannot comment on the performance of other oils in their engines. This is a fair statement. The reality is that the Shell and Valvoline oils of the same specification (viscosity, API and SAE ratings, synthetic or not) are very similar. ( I do have my bullet proof vest on )."

then is there a reason why Mazda gives us 5w20 but not the rest of the world? if its as good as you said (or the Dr. Hass said) everybody should get that "recommendation"

it is true that 5w20 flows easier, it doesnt require as much "force" to push it around.

but also, its strength is just pathetic.

Flow is key, but strength is also important.

Remember one thing : We're the only "country" that has engines breaking down left & right. Well, China has a lot of engine failures too, but its due to poor quality gas that they use and thats different story.

People who gone thru 5000-7000 miles every oil change : do you think most people can tell that their engine "is not working well" ? to most of them, as long as it runs, it starts, then its ok ! No one will "suddenly" decided that he/she should go have a compression test just to see how healthy their engines are.

Even I didnt really "feel" that my engine was bad, I know it had problem(random stalling) The rotor went down from 7.4 psi to 5.8. it runs. I didnt feel anything with it. it still works. it still runs. For the first 15 or 20 thousand miles, the first engine uses 5w20. it could be OMP rate was too low, who knows.

Lets look at this "again"

Lets look at heavier version.

Yes, all oil passed more of less the same requirements. but we know those spec is just the "bare minimum"

Anybody notice one thing? Its ONLY mid-lower end range auto makers would recommend lower weight oil. while MOST top end auto companies, they recommend heavier oil.

Why ?

Take Ferrari as an example, they recommend 60 Weight oil for their engines ~ ! They dont care about CAFE much cuz their cars getting 8 mpg anyway. so they want to make sure that their engines will last forever.

Take a look at the chart on Quakers State and see which company recommends which, you will know what Im talking about.

One more thing, in the old"er" days, Mazda does not gives out a "recommended" grade to use. they just give you a chart and "use THESE ITS ALL OK". but ever since CAFE rules kick in, they have to get the best MPG as possible, who gives a crap about engine life anymore !!!!! Its very hard to see modern (anything after year 2000, for example) with over 150K miles on them.

Now look at this picture from my FC's owner's manual :

(Click the pic below to see it, #1)

Temperature range anticipated before next oil change :

go 5w30 if your oil will see LOWER than 0 Celsius (32f)

Whats the "widest" range? 20w50.

Now lets take a look at "our" 8's chart (???)

(Click the pic below to see it, #2)

To some people, this chart simply means "5w20 is the ONLY thing that works for RX-8". and I guess thats where most engine failure came from.

...perhaps people will finally get their 20W-50 heads out of their collective asses...

I'm a little confused by your post. Correct me if I'm wrong but last I recall I thought you used 20w-50? This is why I thought it was relevant. Also my Mazda book for my 2006 does call out a recommended, only 5w-20, no chart. Lastly, there is some conflicting points then based on what the companies say is good, and what apparently this author says is better.

The oil company says 5w-50 syn is their oil for "cold temp pumpability"? The latter weight has nothing to do with cold temp, the 5w is what has to do with cold temp. It doesn't matter if it's 5w-20 or 5w-50, both start up weight the same viscosity. The 20 versus 50 is for operating temperatures and using his example, 30 is the ideal range. Any thicker is for racing use based on his expertise. Only experimentation will tell but I have to agree based on my experience, 50 is overkill and means less oil flow which results in less lubrication coverage since the whole idea is for better flow. He even leans towards the thinner oils than thicker for recommending.

As for why our vehicles break down so much, there are a crap load of reasons. Most people don't know how to take care of their car or slack on it. The most common cause is overheating, which is not due to the oil, it's due to the cooling design

Quote - Your engine is not producing much heat at low RPM and low BHP output. The production of heat is relatively slow. It can easily be transmitted to your cooling system. The problem is that your cooling system has trouble getting rid of the heat. The oil and the coolant will slowly rise in temperature. They both rise together. The increase is no big deal for your oil. It goes to 220, then 230 F. The problem is that the cooling system can only handle heat up to 230 F. After that you overheat the cooling system and the car must be shut off. The oil never got that hot, It was just that the water got a little hotter than its system design.

As for Ferrari....

Quote - "Ferrari recommends Helix Ultra Racing 10W-60 “for hot climate conditions racing type driving on tracks”.

Again, that is racing which is impractical for road use. Is exactly why the author leans toward thinner oil.

Millers do a 10w-60

I don't see how a general, or "collective," conclusion is warrented without RX8-specific data. Particularly given this information was out there for sometime.

As I see it, all of the the above speculation are hypotheses to be tested in the RX8.

I suppose that most of us need to make a decision now and cannot afford, nor have the experience to do the work necessary to come to a conclusion.

Personally, I will continue to fillup with 5w30 Mobile1 and top off with 10w30 or 10-40 synth. That is what I have done from the begining.

Say it to those zillion rx-8 owners that use nothing but 5w20 with messed up engines.

oh yea I used to believe the 5w20 bullshit, and guess what, damages has been done and there is nothing I can do to reverse it. Switch to 5w30, then 5w40 finally 20w50 prolonged my engine life, but still. nothing can reverse it. so yea it still "KABOOOOOOM!" on me.

maybe you should go try a compression test on your engine ? and see what kind of # you're pulling.

never heard of it. maybe some UK brand ?

Quakers state has 60wt oil.

Here are some good mentions in regards to thicker oil near the end of the article...

Quote - I have some stories that I collected. First, my architect drives a big SUV. He was running with Mobil 1 brand 15W-50. He changed it to Pennzoil Multigrade (mineral oil based, non-synthetic, cheap) 5W-20 at my suggestion. His gas mileage went from 10 to 13 MPG around town. What really impressed him the most was the “robust” increase in “get up and go.” He changed from a thick synthetic to a thin mineral oil. His venue is stop and go city traffic in Florida, mostly short trips. The oil just never got that hot to require a 50 weight oil. Short trips means that the oil temperature never gets up to the normal operating range. It was too thick on short trips and too thick when it did get up to temperature.

The lower temperatures he was seeing occurred because of reduced friction and internal drag and higher oil flow.

One of the members of the Ferrari Chat web site went from a 40 to a 30 weight oil in his Ferrari 355 for racing in Texas. He noticed a drop in temperature but no change in oil pressure. This may seem odd but really makes perfect sense. Since the 30 weight oil is thinner he got better flow and therefore better cooling. The oil was at a lower temperature so it was not as thin than it would have been at the previous higher temperature. Cooler engines last longer. Fact: The higher the temperature, the greater the wear, all other things being equal.


You make the call.

Props to the OP for this post whether repost or not. I would of been too lazy to read all the zillion threads on oil here to find it. But I'm definitely looking into synthetics now.