Oil oil brand and weight for 24k miles

[robin2660]

Question then ...

How does a thinner oil lubricate less?

Also, anyone care to cite any professional references to support the need for a certain weight oil for turbocharged engines?

 

[robin2660]

Another question ... does anyone know the temperature of the turbo turbine housing through which the oil is passing? I think, otherwise, we're just guessing what should be the correct oil weight.

BTW, found this great link ... am in the middle of reading it .... http://www.supramania.com/aehaas/

 

[jabba]

Question then ...

How does a thinner oil lubricate less??

My view on this is about degradation, not lubrication. Many new cars now take 5W20, since new engines have tighter tolerances and oil has to flow to get to where it has to go. This weight oil helps also them meet CAFE standards. So nothing wrong here, but a lot of these cars are non-turbo. But that doesn't mean it's not good for a turbo, I'm just going by gut feel.

The W20 should have lower molecular weight fractions than a W30 or W40, hence it might degrade faster, and hence it might also have more volatiles. To me it spells bad news. Turbos spin at tens of thousands of rpms, I'd want to make sure the oil can handle the shear. Maybe that's why my manual says to use a W30 grade, not a W20.

 

[robin2660]

Anybody read the supramania link yet?

 

[MSMS3]

Anybody read the supramania link yet?

Yes. I did read every one of the articles. Good information for normally aspirated engines and good support for the superior performance of synthetics, especially during startup (and particularly cold weather startup) when most engine wear takes place.

The Ferrari and the Ford Expedition discussed in those articles (the two vehicles owned by the author) are not turbocharged, however, and there is no discussion whatsoever of the extra protections needed when engine oils pass through the center bearings of a turbocharger under WOT full load operating temperatures. Oil temps in the Ferrari and Expedition engines did not exceed a bit over 300 degrees. If high boost turbocharged application oils are discussed in those articles, I guess I missed it.

BTW: There is a thread here where MS3 owners have discussed the exhaust gas temperatures of these engines under different operating parameters. They vary depending on whether measured at the exhaust manifold or at the wideband bung in the downpipe, getting cooler depending on where measured. Temps in the exhaust manifold, which would approximate the temps inside the turbo's exhaust side where the center shaft journal bearings are located are as high as 1400 degrees and temps in the upper part of the down pipe as high as 1200 degrees, according to the measurements made by our members.

 

[robin2660]

Ok, here's the deal. I'm not an expert. I'm here to learn. Thus, I ask questions. So, if the turbo's smoking due to seals leaking, it seems to me that the flow is backing up and causing excess pressure behind the seals, and thus causing oil to get past them.

Now, as I understand it, lighter weight oil will have less pressure and more flow, all else being equal. More flow equals more lubrication and more cooling, according to everything I've gathered from Dr. Haas. All this makes sense to me. So, why would one use a heavier weight oil for a turbo? If all that heat causes the oil to break down, all you do is change the oil more often. You don't use heavier oil to avoid it breaking down, because you defeat the lubrication and cooling effects of the oil.

Regarding exhuast gas temperatures ... I'm not sure they apply directly, because that's not the temperature of the center shaft of the turbine housing, which is not only lubricated with engine oil, but also water cooled. I'd like to know what that temperature might be.

Now, we choose engine oil based on what it does for the engine, not the turbo. What would you prefer to take care of most, the motor or the turbo?

Is there anything wrong with my thinking so far?

 

[60181]

Research the banjo bolt aka "bnoon bolt fix" and try that.

Ok, here's the deal. I'm not an expert. I'm here to learn. Thus, I ask questions. So, if the turbo's smoking due to seals leaking, it seems to me that the flow is backing up and causing excess pressure behind the seals, and thus causing oil to get past them.

 

[MSMS3]

Ok, here's the deal. I'm not an expert. I'm here to learn. Thus, I ask questions. So, if the turbo's smoking due to seals leaking, it seems to me that the flow is backing up and causing excess pressure behind the seals, and thus causing oil to get past them.

Now, as I understand it, lighter weight oil will have less pressure and more flow, all else being equal. More flow equals more lubrication and more cooling, according to everything I've gathered from Dr. Haas. All this makes sense to me. So, why would one use a heavier weight oil for a turbo? If all that heat causes the oil to break down, all you do is change the oil more often. You don't use heavier oil to avoid it breaking down, because you defeat the lubrication and cooling effects of the oil.

Regarding exhuast gas temperatures ... I'm not sure they apply directly, because that's not the temperature of the center shaft of the turbine housing, which is not only lubricated with engine oil, but also water cooled. I'd like to know what that temperature might be.

Now, we choose engine oil based on what it does for the engine, not the turbo. What would you prefer to take care of most, the motor or the turbo?

Is there anything wrong with my thinking so far?

Some things are not as they might seem logically. Virtually every high performance car manufacturer with turbocharged engines either recommends synthetic oil or the cars come from the factory with synthetics. Those that don't usually recommend use of synthetics once the break in oil (typically conventional mineral spirits based) is removed at the first oil change.

I'm not trying to argue or persuade. These are just basic facts determined over decades of use in the industry. This is my fourth high performance turbo car -- the others were Saabs and a Volvo. But I'm not an expert either.

I think it is the reasoning of manufacturers, including Mazda in their bulletin to dealers that thinner oils do tend to get past the seals more readily and that synthetic oil is less likely to smoke than conventional oils when it does get past the seals and enters the exhaust stream, hence the recommendation for 5-40 synth if turbo seal leak is an issue. That bulletin was for certain specific VIN numbers and year models as there have been, I believe, at least three changes in our turbo design by Mazda since the car first appeared as an '07 model, and perhaps the latest generation K04's do have better designed seals.

You are right that there is a water jacket in the turbo housing and it helps tremendously. And the center shaft (and therefore the oil going to the journal bearings) does not see the full heat (or at least until it gets fully heat soaked by prolonged WOT), of the exhaust flow. I don't know any realistic way to measure the temps transmitted to the center shaft, but it is going to be much hotter than any NA engine.

There is yet another concern regarding the K04 turbo design in our application and that is that the center shaft is only 5mm in diameter and has been shown in other applications (VW and Audi) to soften if the turbo is operated at much over 5,800 rpm due to excessive heat generated inside the turbo as a result of trying to push more boosted air through the compressor side than the flow rate of the turbo -- it becomes its own heat engine separate and distinct from the exhaust heat on the turbine side.

The VW-Audi K04's were getting hot enough to experience center shaft failure despite water cooling. Here is the report obtained from a Mazdaspeed owner "enganear" obtained from his post on another forum. This is based on research done by Neuspeed, a highly respected aftermarket tuner/vendor for other platforms (not Mazda so far). They were having a rash of K04 turbo failures on the VW-Audi B5 four cylinder turbo engine and commissioned a study of the problem. They suspended their sales of K04's until they were able to determine what was happening.

Report is attached. Center housing excessive heat is a problem for this turbo when pushed beyond 5,800 rpm. Our K04 is a bit different and, as stated above, has been modified several times during the production run. However, to my knowledge the center shaft is still only 5mm in diameter. It needs all the high grade oil we can supply. I do not go so far as to accept Neuspeed's recommendations on oil weights as high as 20w50 in summer. Our engine requirements may be signficiantly different that VW-Audi and we may need thinner oil for proper flow in some of the very tiny oil orifaces in our cylinder head and camshaft, and to allow proper drainage back into the block for proper lubrication of the crankshaft, etc.

But this illustrates the point that turbocharged engines benefit from use of synthetic oils and we need to be thinking about the effect of heat on the oil in that line returning to the engine from the turbo.

Sorry for the long post. These are just things that cause me to run a bit heavier full synthetic and cause me to stay out of the throttle much past about 5,500 rpm.

 

[Saskatchewan17]

For you? Shell Rotella T6 5w-40. Stuff is specially formulated for heavy duty engines which include fleet diesels, which are much like MZR DISIs (Direct injection, turbocharged).

 

[robin2660]

So, the question remains, do we choose an engine oil best suited to engine longevity, or for the turbo? Ideally, it would be for both but I have not read anything to convince me heavier weight oil is more beneficial to either engine or turbo. Lighter weight oil = better flow = better cooling and lubrication. This is what I have learned.

Regarding the Neuspeed article - the gist of that seems to be concerning overheating and shaft warping due to operating under boost over 5800 rpm. Personally, as a DD, my car rarely, if ever sees that kind of engine speed.

For all the concern I'm a bit surprised all the mod-happy people haven't bothered to install (as per Neuspeed's recommondation) a gas temperature probe into the turbine housing.

 

[what_the]

Lighter weight oil doesn't = better lubrication. It is all somewhat relative. Lighter oil has a lower viscosity so, yes it does flow easier, but as for lubricating better that is more determined by the bearing design. Tolerances, loading(P x V), and bearing wear characteristics all factor in to the oil weight chosen. To thin of an oil and the oil film layer will be to thin and can result in metal to metal contact or local heating of the oil due to excessive shear in the oil film. It has been a couple of years since I took the bearing and machine design class, so some of my terminology might not be correct. Also I can go dig up the equations out of my old text book if anyone cares.

 

[robin2660]

Lighter weight oil doesn't = better lubrication. It is all somewhat relative. Lighter oil has a lower viscosity so, yes it does flow easier, but as for lubricating better that is more determined by the bearing design. Tolerances, loading(P x V), and bearing wear characteristics all factor in to the oil weight chosen. To thin of an oil and the oil film layer will be to thin and can result in metal to metal contact or local heating of the oil due to excessive shear in the oil film. It has been a couple of years since I took the bearing and machine design class, so some of my terminology might not be correct. Also I can go dig up the equations out of my old text book if anyone cares.

I think you're missing the point though. It's better cooling we're looking for. Also, lighter weight oil, providing better flow and less pressure would, it seems to me, result in less seal leakage.

 

[jabba]

I think you're missing the point though. It's better cooling we're looking for. Also, lighter weight oil, providing better flow and less pressure would, it seems to me, result in less seal leakage.

I think he got the point correctly, you just have to take it a step further: so because an oil like a W20 can make a thinner hydrodynamic wedge between the bearings, this might mean that you can increase your chance of metal-metal contact if the oil degrades and shears. Now this can also affect cooling: since the oil is heated by the frictional forces, if there is less oil present between the bearings, it might not be able to carry the heat away. So there would not be better cooling in that case.

This all hinges on the W20 shear thinning and degrading, though. Maybe the additive packages in the W20 make it very stable. I just don't know. So I'm not taking that chance.

 

[gogogomoveit]

It is amazing to me that something that is called out so explicitly in the instruction manual, can be such a hot topic for discussion. Granted Mazda designed that damn engine and have a boat load more (and valid, not hearsay)test data than anyone of us here, and spec'd out the required DINO, Not synthetic oil viscosity and change interval for expected consumer usage, and yet be confident enough that they wont have waves of turbo failure recall due to insufficient lubrication.

Dont get me wrong, discussion is all good, but what is there to argue really? Buy synthetic at 5W-30 and call it the day?

 

[what_the]

I agree with gogogomoveit's point that Mazda knows more since they designed the engine, but the 5W-30 spec oil can mean several things unless a specific brand is named. 5W-30 oil from one brand to another doesn't necessarily match the viscosity of another brands 5W-30. Hell my 0W-30 oil tests closer to or thicker than some synth 10W-40 oils. I feel that is a point to argue right there.

 

[gogogomoveit]

I agree with gogogomoveit's point that Mazda knows more since they designed the engine, but the 5W-30 spec oil can mean several things unless a specific brand is named. 5W-30 oil from one brand to another doesn't necessarily match the viscosity of another brands 5W-30. Hell my 0W-30 oil tests closer to or thicker than some synth 10W-40 oils. I feel that is a point to argue right there.

http://www.bobistheoilguy.com/visc.html

The viscosity of the oil has to be measured and matched to the SAE viscosity chart. 30 grade oil has a viscosity of 9.30-12.49 centistokes, which may translate into your experience of different apparent viscosity of 30 oils.

http://www.bobistheoilguy.com/cms/index.php?option=com_content&view=article&id=53&Itemid=61

Great article. Everyone who is interested in oils should digest this throughly

 

[robin2660]

http://www.bobistheoilguy.com/visc.html

The viscosity of the oil has to be measured and matched to the SAE viscosity chart. 30 grade oil has a viscosity of 9.30-12.49 centistokes, which may translate into your experience of different apparent viscosity of 30 oils.

As I was saying. So, recommending 10W-30 without knowing the actual viscosities is a shot in the dark. As I mentioned earlier, some xW-20 oils are close to 10cSt., which makes them as appropriate as some xW-30 oils.

But also note that some of these xW-30 weight oils are also in the 12cSt range, which is inappropriately thick. I think a 9.5cSt xW-20 weight oil would be a better match than a 12.0cSt xW-30 or xW-40 weight oils that are in the 14cSt range.

By the way, people who drive in the winter should be using the lowest multi-weight oil possible - not 10W-XX, but 5W or even 0W-XX since the majority of engine wear occurs at startup. This makes me think of getting a pre-oiler like the one Amsoil markets. http://www.smartsynthetics.com/products/amsoil-prechargers-amk01-amk02.htm

But I could be way off here ... just going by what I'm learning ....

 

[MSMS3]

From an old Saturday Night Live skit routine:

"This conversation has become tiresome."

I do not believe that further discussion of this topic would be constructive for me.

I live in the Deep South. It rarely freezes here. I'm content to run 5W30 full synthetic all year here due to my climate and due to the relationship between Mazda's realization and correction of its error regarding the needs of the turbocharged MZR engine, and the well-developed and rational views of some of our highly experienced forum members and the performance turbo community at large. I'm not smoking even with a catless dp/rp so I see no reason to go to 5W40 but would do so if any early signs developed suggesting seal leakage (doubtful after 31,000 miles, about 20,000 of which has been with all mods below. I drive the piss out of my car.

Having said that, I'm unsubscribed from this thread. In the quaint language of my region: Y'all have fun."

 

[robin2660]

After tons of reading and listening to you guys here, I'm starting to believe there is a lot of myth, lore, and religion concerning motor oils. Those of you who insist Synthetic is a must have yet to prove a reliable argument.

No one here has bothered to cite resources for my reading ... at least none that I've already read. Where's all the evidence that mineral-based oils are going to ruin the engine on these turbo cars? (uhm)

What I've learned: Synthetic oil lubricates better. It also doesn't break down. Theoretically, anyway, you could use that oil indefinitely if you could clean it adequately. But, no one has proved that using mineral oil doesn't lubricate sufficiently/adequately, or leads to excessive engine wear, especially when adhering to liberal oil change intervals. I haven't seen any. Plus, not everyone drives their cars hard. I know I don't.

Even so, most of you aren't going to keep your cars long enough that it matters. So, why spend the extra money on synthetic oil?

Another funny thing is, how everyone backs up Mazda's advice of using 5W-30 instead of 5W-20, "because Mazda has done tons and tons of research so they know what's best ..." blah blah blah ... and, yet, they contradict themselves that Mazda doesn't know what's best when they recommend mineral oil.

If you guys were truly concerned about wear and tear, and were rational about it, you wouldn't drive your cars so hard. Another thing you might do, that makes perfect sense considering over 80% of the wear and tear on your engines is at startup, is to install an engine pre-oiler! How many of you have bothered to ad that to your list of mods? To me, spending a couple hundred bucks on a pre-oiler would far outweigh the benefits of synthetic oil (and would be paid for with 4 oil changes considering the price of synth. oil). Your motor would last longer and suffer less wear/tear from this mod than the improvements gained from using synthetic vs mineral-based oil.

So, I'd like to see some scientific evidence instead of beliefs, suggestions, and innuendo. Otherwise, I'm not convinced it's worth it.

 

[MSP300]

listen dude instead of doing all this reading why dont you try different oils (brand and grade) and see which one suits you best

a lot of this guys tried different oils and they tell u which one they liked the most, i know guys who use 10w-40, 5w-40 in their cars and they have no problems

i personally prefer amsoil 5w-30, i can feel that my car runs better and it doesn't burn as much oil as other brands do(mobile one for example)

no body is gonna do scientific research just so they can prove it to you that 5w-20 is better than 5w-30