Castrol Edge Clearance!?!

[Lt. Leary]

I happened to be at my local Auto Zone today and happened by the oil aisle. Castrol Edge 0W-40 5 quart bottle is on clearance for $10! So naturally I bought them out (3 bottles left), but why are they on clearance in the first place? I just bought two from Amazon for $23 a piece, which is down from the retail price of $38 or so. Is Castrol discontinuing this line of oil for something different?

[bNks334]

Originally Posted by Lt. Leary

I happened to be at my local Auto Zone today and happened by the oil aisle. Castrol Edge 0W-40 5 quart bottle is on clearance for $10! So naturally I bought them out (3 bottles left), but why are they on clearance in the first place? I just bought two from Amazon for $23 a piece, which is down from the retail price of $38 or so. Is Castrol discontinuing this line of oil for something different?

The 5-30 edge euro formula is specd perfectly for the n54/n55. The 0-40 is a little thicker, but will work just fine as well.

It's just an annual clearance of old stock... Castrol updates their bottle with new advertising and the oil certs also change over time.

[Dackelone]

Originally Posted by bNks334

The 5-30 edge euro formula is specd perfectly for the n54/n55. The 0-40 is a little thicker, but will work just fine as well.

BMW says your can use any of these viscosity oils: 5w30, 5w40, 0w30, 0w40, in your owners manual. The oil should also be rated LL1 for the US market fuels. LL4 for the rest of the world.

A 0w40 oil has a wider temp range than say a 5w30 oil. The 0w40 oil will flow better when cold(or at colder temps) than a 5w30 oil. The 0w40 oil will also be thicker at high temps.

It's just an annual clearance of old stock... Castrol updates their bottle with new advertising and the oil certs also change over time.

Yep.

[Iron Man]

Originally Posted by Lt. Leary

I happened to be at my local Auto Zone today and happened by the oil aisle. Castrol Edge 0W-40 5 quart bottle is on clearance for $10! So naturally I bought them out (3 bottles left), but why are they on clearance in the first place? I just bought two from Amazon for $23 a piece, which is down from the retail price of $38 or so. Is Castrol discontinuing this line of oil for something different?

I picked up several one quart bottles of Castrol 0W-30 for $0.25/bottle. Nothing beats a $1.75 oil change. Autozone and AAP both typically have year end closeouts to clear out inventory. Castrol doesn't usually give rebates like Mobil 1 and Shell, but they do have great year end deals.

[david in germany]

Originally Posted by Dackelone

BMW says your can use any of these viscosity oils: 5w30, 5w40, 0w30, 0w40, in your owners manual. The oil should also be rated LL1 for the US market fuels. LL4 for the rest of the world.

A 0w40 oil has a wider temp range than say a 5w30 oil. The 0w40 oil will flow better when cold(or at colder temps) than a 5w30 oil. The 0w40 oil will also be thicker at high temps.




Yep.

Just wanted to ask you what you are now running since Castrol pulled the LL-04 from the German shelves? Looking for oil for my next change as I have already gone through my 30l I had on hand..

[bNks334]

Originally Posted by Dackelone

BMW says your can use any of these viscosity oils: 5w30, 5w40, 0w30, 0w40, in your owners manual. The oil should also be rated LL1 for the US market fuels. LL4 for the rest of the world.

A 0w40 oil has a wider temp range than say a 5w30 oil. The 0w40 oil will flow better when cold(or at colder temps) than a 5w30 oil. The 0w40 oil will also be thicker at high temps.

Yep.

My comment was to point out that the 5-30wt Castrol euro blend matches BMW's N54/N55 5-30wt blend spec for spec. Check the Cst and Cp and VI ratings. those are what matter. Oil's shelf wt is just a category of kinetic viscosity taken at temps LOWER than what our cars normally operate at...

Without getting into a debate over oil specs, my opinion is that while 0-40wt might be better for a daily driven car in the winter, 5-30wt (with proper specs) is the better oil to use for performance driving during the summer when cold start temps are less relevant. 5-30wt oils will maintain their shear resistance and viscosity better at the higher loads seen in an n54/n55 engine. These higher loads produce oil temps at the sump of close to 300f and probably 400+ in the bearings (the flash point of most top quality synthetics). Running a thicker weight oil will just increase oil pressure and generate more heat. Ultimately the heavier weight oil with higher VI (more added polymers) will break down faster in these extreme conditions. A higher viscosity spread results in a weaker oil even if it looks better on paper @ the tested 100c lol

[Dackelone]

Originally Posted by david in germany

Just wanted to ask you what you are now running since Castrol pulled the LL-04 from the German shelves? Looking for oil for my next change as I have already gone through my 30l I had on hand..

I have been using this Castrol(Castrol EDGE Turbo Diesel 5W-40 Motoröl) oil bought from Amazon.de I'm pretty sure its still LL4 rated but I have to double check my old bottle(s). Even IF it's LL1... that doesn't bother me that much since I change my oil at least every 8K kms or sooner. Normally I change it twice a year - since I don't daily drive my 135i.

https://www.amazon.de/dp/B01BBTA90O/...4K579XN8&psc=1

Dack

[bNks334]

Originally Posted by Dackelone

I have been using this Castrol(Castrol EDGE Turbo Diesel 5W-40 Motoröl) oil bought from Amazon.de I'm pretty sure its still LL4 rated but I have to double check my old bottle(s). Even IF it's LL1... that doesn't bother me that much since I change my oil at least every 8K kms or sooner. Normally I change it twice a year - since I don't daily drive my 135i.

https://www.amazon.de/dp/B01BBTA90O/...4K579XN8&psc=1

Dack

you explained it well back in 2011 lol:

I think this document is written for the US market in mind. Basically in a nutshell...

LL-1 oils are for high sulfur content fuels - as in USA fuels.

LL-4 oil is for low sulfur content fuels - as in Germany/Europe fuels


Back in the early to mid nineties BMW had a huge problem with the high sulfur fuels in the USA with their V8 engines. The high sulfur caused many BMW V8 engines to loose compression and rough running. It had to do with teh special cylinder coatings - that the high sulur would damage the way the pistons rings would seal against the cylinder wall.

It became so bad that BMW increased the garranty to 10year/100K miles (only for these effected v8 engines) - and had an open "service campaign" (NOT a recall!) for any 530i, 540i, 730i or 740i owner to have their BMW dealer REPLACE their engine will a different engine block deisgn - as to not have future problems with high sulfur in the fuels.

This is what caused BMW to develop special oils for each market.


Dackel

[Iron Man]

Originally Posted by bNks334

My comment was to point out that the 5-30wt Castrol euro blend matches BMW's N54/N55 5-30wt blend spec for spec. Check the Cst and Cp and VI ratings. those are what matter. Oil's shelf wt is just a category of kinetic viscosity taken at temps LOWER than what our cars normally operate at...

Without getting into a debate over oil specs, my opinion is that while 0-40wt might be better for a daily driven car in the winter, 5-30wt (with proper specs) is the better oil to use for performance driving during the summer when cold start temps are less relevant. 5-30wt oils will maintain their shear resistance and viscosity better at the higher loads seen in an n54/n55 engine. These higher loads produce oil temps at the sump of close to 300f and probably 400+ in the bearings (the flash point of most top quality synthetics). Running a thicker weight oil will just increase oil pressure and generate more heat. Ultimately the heavier weight oil with higher VI (more added polymers) will break down faster in these extreme conditions. A higher viscosity spread results in a weaker oil even if it looks better on paper @ the tested 100c lol

Not sure I necessarily agree with all you've said. Though any oil that is LL-01 rated (and A40, 229.5 etc.) will be an excellent oil that is resistant to shearing (high HTHS), with low NOACK and low pour points. You can create a relatively high VI of an oil by using a high quality blend of Group IV/V base stocks and not using a lot of VII. I doubt there is really much of a performance difference in any 5W-30/0W-30/5W-40/0W-40 that is on the LL-01/229.5/A40 approval list, since it has to be an excellent oil to even make the list (shear stable, low NOACK, etc.).

[bNks334]

Originally Posted by Iron Man

Not sure I necessarily agree with all you've said. Though any oil that is LL-01 rated (and A40, 229.5 etc.) will be an excellent oil that is resistant to shearing (high HTHS), with low NOACK and low pour points. You can create a relatively high VI of an oil by using a high quality blend of Group IV/V base stocks and not using a lot of VII. I doubt there is really much of a performance difference in any 5W-30/0W-30/5W-40/0W-40 that is on the LL-01/229.5/A40 approval list, since it has to be an excellent oil to even make the list (shear stable, low NOACK, etc.).

Yeah, I get what you're saying. I was just trying to say that thicker wt oil isn't necessarily any better for high load when it comes to your typical shelf oil. If you've seen the "rat" oil analysis list his testing shows how some of the tested oils perform remarkably better in regard to maintaining film strength in high shear conditions. They were all 5-30 oils with 40wt performing worse.

Then you look at the few specialty oils that offer true Group V base and you see they lack in other areas... so it's pretty much pick your poison in that regard. There are plenty of excellent oils that meet A40 requirements, but don't meet LL-01. Mobil 1? the Sulpher ash content Dackelone brought up is an important piece of ll-01 too... Can't find the actual specs for what makes an oil LL-01 though other than the minimum of 3.5 cp (which mostly limits you to heavy 30wt oils and light 40 wt oils).

[Iron Man]

Originally Posted by bNks334

Yeah, I get what you're saying. I was just trying to say that thicker wt oil isn't necessarily any better for high load when it comes to your typical shelf oil. If you've seen the "rat" oil analysis list his testing shows how some of the tested oils perform remarkably better in regard to maintaining film strength in high shear conditions. They were all 5-30 oils with 40wt performing worse.

Then you look at the few specialty oils that offer true Group V base and you see they lack in other areas... so it's pretty much pick your poison in that regard. There are plenty of excellent oils that meet A40 requirements, but don't meet LL-01. Mobil 1? the Sulpher ash content Dackelone brought up is an important piece of ll-01 too... Can't find the actual specs for what makes an oil LL-01 though other than the minimum of 3.5 cp (which mostly limits you to heavy 30wt oils and light 40 wt oils).

Please see the attached Lubrizol chart comparing MB 229.5/LL-01 to SN ratings. LL-01 requires a minimum HTHS (shear stability) of 3.5, which pretty much requires a "heavy" 30wt oil or a 40wt oil. It also requires a 10.0 TBN minimum. Mercedes 229.5 requires a NOACK maximum of 10%, so all of the Euro specs (Add A3/B4 as well) together are way above and beyond any US API requirement and not easy to meet (pretty much Group III/IV/V oil). I would think the excessive use of VII really pertains to oils that probably have "cheaper" base stocks and a very high VI rating.

Also, if you do any research on BITOG, they have pretty much disproven the "Rat" test and shown it is not applicable to an oil's performance in an actual ICE and the associated engine wear. https://bobistheoilguy.com/forums/ub...ts#Post3854023

I would say anyone worried about their oils performance, should really have a UOA done to see how it performs for their specific driving habits and particular vehicle/driving conditions.

[bNks334]

Please feel free to correct me because this is all stuff I've concluded by looking at the same sources as you.

Originally Posted by Iron Man

Please see the attached Lubrizol chart comparing MB 229.5/LL-01 to SN ratings.

That Lubrizol chart isn't really relevant at all. I am more talking about choosing the right oil weight over using extending oil changes. The only category I'd be concerned about is "wear" and "wear" is relative...

Originally Posted by Iron Man

LL-01 requires a minimum HTHS (shear stability) of 3.5, which pretty much requires a "heavy" 30wt oil or a 40wt oil.

Right, I've already said this. My point is oil isn't one-way. You can't just put a thicker weight oil in your engine because it's "better." There is also a maximum where all you'll do is reduce performance... cP directly correlates to how well an oil flows.

My main point being that using a proper spec'd 5-30wt oil for performance driving will probably be better than using a heavier weight 0-40wt oil to "add protection." Seems counter intuitive, buts it's really not when you consider engine tolerances can't just increase to accommodate a thicker oil film (higher cP)... and then also consider that, in general, the 5-30wt will maintain its properties better under load. A 10-30 would probably be even better for performance driving.

Originally Posted by Iron Man

It also requires a 10.0 TBN minimum.

Good to know, but this doesn't really have any bearing on what I am saying. It might make a good argument for using oil x over oil y when following BMW's LL-01 oil change interval though... most of us aren't interested in 30km oil changes outside of warranty.

Originally Posted by Iron Man

Mercedes 229.5 requires a NOACK maximum of 10%, so all of the Euro specs (Add A3/B4 as well) together are way above and beyond any US API requirement and not easy to meet (pretty much Group III/IV/V oil).

Not sure what you're even referring to here... US API just gives us a rating of an oils kinetic viscosity. This is exactly what I am saying NOT to rely on when choosing oil to put in your engine.

I do agree a lower NOACK value is good for our cars since they run HOT.

Again, a 0-40 oil will probably have higher PAO's and will probably have a HIGHER NOACK % than the same exact oil but in 5-30wt... which would you choose?

This is kind of what RAT concluded with his volatility tests, which is the only reason I brought them up. Now consider the 5-30 also has a more ideal HTHS/cP value for the given engine bearing clearances.

Originally Posted by Iron Man

I would think the excessive use of VII really pertains to oils that probably have "cheaper" base stocks and a very high VI rating.

Which is pretty much every shelf oil out there. Which is what we are discussing...

Originally Posted by Iron Man

Also, if you do any research on BITOG, they have pretty much disproven the "Rat" test and shown it is not applicable to an oil's performance in an actual ICE and the associated engine wear. https://bobistheoilguy.com/forums/ub...ts#Post3854023

I know, his tests were retarded. I shouldn't have even brought it up. He did make some good points though about traditional additives like zinc and prosperous being more detrimental in large quantities than good for daily driving.

He also brought up good points about matching proper oil to an engine. You need an oil that ensures you maintain proper oil pressure without increasing it unnecessarily. I'm not saying 0-40 wt oil won't work... just that it may not be any "better" for all the aforementioned reasons.

And yeah, maybe the Porsche and MB spec'd oils are of the same "high quality" as BMW LL-01 oil, but you can't just make a blanket statement that an A40 oil is good oil so it's ok to use in our BMW's... engine tolerances don't just get bigger unless you bend something.

Originally Posted by Iron Man

I would say anyone worried about their oils performance, should really have a UOA done to see how it performs for their specific driving habits and particular vehicle/driving conditions.

I agree a UOA can tell you how well an oil is maintaining its properties over time. However, permanent shear and degradation of oil additives is only part of the picture. A UOA can't tell you what the oils is doing as it temporarily shears under high load.

[Iron Man]

Originally Posted by bNks334

My main point being that using a proper spec'd 5-30wt oil for performance driving will probably be better than using a heavier weight 0-40wt oil to "add protection." Seems counter intuitive, buts it's really not when you consider engine tolerances can't just increase to accommodate a thicker oil film (higher cP)... and then also consider that, in general, the 5-30wt will maintain its properties better under load. A 10-30 would probably be even better for performance driving.

I still disagree and I doubt we will ever agree. My point was that any oil with multiple certifications, like Castrol 0W-40, is going to be an excellent oil and most likely better protection for your engine than a 5W-30. I don't see why you think a 5W-30 would perform better at temperature and under load. The higher viscosity will protect better at temperature and the 0W oil would flow better at start-up, where most engine wear occurs. Either way, a 5W-30 with the same certifications as a 0W-40 will probably perform almost identically in service and your engine will never know the difference. If BMW says your engine can use either oil (with the same approval), then they designed the engine to handle either oil. I doubt the engine tolerances are affected by either weight.

[david in germany]

Originally Posted by Dackelone

I have been using this Castrol(Castrol EDGE Turbo Diesel 5W-40 Motoröl) oil bought from Amazon.de I'm pretty sure its still LL4 rated but I have to double check my old bottle(s). Even IF it's LL1... that doesn't bother me that much since I change my oil at least every 8K kms or sooner. Normally I change it twice a year - since I don't daily drive my 135i.

https://www.amazon.de/dp/B01BBTA90O/...4K579XN8&psc=1

Dack

Thanks man, I know that any LL-04 should do but I was skeptical on the 5W-40 as it is a bit thicker on the high end.

[bNks334]

Originally Posted by Iron Man

I still disagree and I doubt we will ever agree. My point was that any oil with multiple certifications, like Castrol 0W-40, is going to be an excellent oil and most likely better protection for your engine than a 5W-30. I don't see why you think a 5W-30 would perform better at temperature and under load. The higher viscosity will protect better at temperature and the 0W oil would flow better at start-up, where most engine wear occurs. Either way, a 5W-30 with the same certifications as a 0W-40 will probably perform almost identically in service and your engine will never know the difference. If BMW says your engine can use either oil (with the same approval), then they designed the engine to handle either oil. I doubt the engine tolerances are affected by either weight.

Now you're saying something that DOES make sense. If two oils both meet BMW's ll-01 spec (there aren't many choices in the US), the engine probably won't care which one you choose. Even if one oil is a 30wt (a thick 30) and one is a 40wt (a thin 40), they will probably be very close in cSt, cP, NOACK, and any other spec we really care about. For a daily driver, you can just throw any of these oils into your car and be fine.

Earlier, you weren't comparing LL-01 to LL-01 oils. You were saying there are non ll-01 oils with "better" specs so it must be ok to put it in our car. I counter argued that they might be "better" but they could also be TOO THICK to put in our engines.

The 30/40/50/60 rating alone doesn't mean anything... There are plenty of 30 wts that aren't good for our engines because they are too thin. It also works both ways though and there are plenty of 40wts that won't work well for our engines either because they are too thick. By your logic, thicker oil is better so we might as well run 0-60wt oil so long as it meets specs for Porsche or Benz. Go too thick and you're actually INCREASING the likelihood of losing the oil film between moving parts (starvation) despite the thicker oil handling loads better.

I thought you also understood I was making the argument for running the 30wt for performance driving. I said this because less polymer is used to create the viscosity spread. As I already said, in general, 0-40 oil has a higher NOACK % than the same exact oil in 5-30wt. Castrol edge euro 0-30 (LL-01 approved) has a noack of 8.3% while the 0-40 is over 10%... again, which would you choose? Apprently BMW says they'll both work just as well in the engine... one will run a little thicker at temp causing higher oil pressure and temps. Both have the same exact HTHS rating of cP 3.5. One is more volatile... seems pretty clear to me which one I'd want to run on track.

http://www.machinerylubrication.com/.../oil-viscosity

A significant reduction in viscosity can result in:
• Loss of oil film causing excessive wear
• Increased mechanical friction causing excessive energy consumption n Heat generation due to mechanical friction n Internal or external leakage
• Increased sensitivity to particle con- tamination due to reduced oil film
• Oil film failure at high temperatures, high loads or during start-ups or coast-downs.

Likewise, too high a viscosity can cause:
• Excessive heat generation resulting in oil oxidation, sludge and varnish build-up
• Gaseous cavitation due to inadequate oil flow to pumps and bearings
• Lubrication starvation due to inadequate oil flow
• Oil whip in journal bearings
• Excess energy consumption to over- come fluid friction
• Poor air detrainment or demulsibility
• Poor cold-start pumpability.

[Iron Man]

Originally Posted by bNks334

Now you're saying something that DOES make sense. If two oils both meet BMW's ll-01 spec (there aren't many choices in the US), the engine probably won't care which one you choose. Even if one oil is a 30wt (a thick 30) and one is a 40wt (a thin 40), they will probably be very close in cSt, cP, NOACK, and any other spec we really care about. For a daily driver, you can just throw any of these oils into your car and be fine.

Earlier, you weren't comparing LL-01 to LL-01 oils. You were saying there are non ll-01 oils with "better" specs so it must be ok to put it in our car. I counter argued that they might be "better" but they could also be TOO THICK to put in our engines.

The 30/40/50/60 rating alone doesn't mean anything... There are plenty of 30 wts that aren't good for our engines because they are too thin. It also works both ways though and there are plenty of 40wts that won't work well for our engines either because they are too thick. By your logic, thicker oil is better so we might as well run 0-60wt oil so long as it meets specs for Porsche or Benz. Go too thick and you're actually INCREASING the likelihood of losing the oil film between moving parts (starvation) despite the thicker oil handling loads better.

I thought you also understood I was making the argument for running the 30wt for performance driving. I said this because less polymer is used to create the viscosity spread. As I already said, in general, 0-40 oil has a higher NOACK % than the same exact oil in 5-30wt. Castrol edge euro 0-30 (LL-01 approved) has a noack of 8.3% while the 0-40 is over 10%... again, which would you choose? Apprently BMW says they'll both work just as well in the engine... one will run a little thicker at temp causing higher oil pressure and temps. Both have the same exact HTHS rating of cP 3.5. One is more volatile... seems pretty clear to me which one I'd want to run on track.

http://www.machinerylubrication.com/.../oil-viscosity

A significant reduction in viscosity can result in:
• Loss of oil film causing excessive wear
• Increased mechanical friction causing excessive energy consumption n Heat generation due to mechanical friction n Internal or external leakage
• Increased sensitivity to particle con- tamination due to reduced oil film
• Oil film failure at high temperatures, high loads or during start-ups or coast-downs.

Likewise, too high a viscosity can cause:
• Excessive heat generation resulting in oil oxidation, sludge and varnish build-up
• Gaseous cavitation due to inadequate oil flow to pumps and bearings
• Lubrication starvation due to inadequate oil flow
• Oil whip in journal bearings
• Excess energy consumption to over- come fluid friction
• Poor air detrainment or demulsibility
• Poor cold-start pumpability.

I was never comparing non-LL-01 oils with LL-01 oils. Since we are talking about BMW here, they are irrelevant. You are incorrect about the NOACK on 0W-40, it is MB 229.5 approved, so it must be below 10%. I believe last I saw it was 9.1%, so 8.3% vs 9.1 is a virtual draw. Also, I said our engines are approved for 30wt and 40wt oils. If I had to choose between the two, I would go with a 40wt oil. There is no 40wt oil too thick for our cars, since then they wouldn't be a 40wt by definition. Once again, calling out a 60wt oil is irrelevant and has nothing to do with my point.

Volatility more to do with extended oil life (and sump size) than running oil at a track. If you want to race and our worried about shearing, choose a racing oil like Motul 300V.

Also, shear resistance of an oil is a function of the HTHS. Since LL-01 requires a 3.5 minimum, almost all Euro oils fall around 3.6-3.8, so once again (0W-40, 5W-30, etc.) with a A3/B4/LL-01/229.5 approval have very similar HTHS and similar shear resistance. If you want better shear stability, go with a racing oil (or maybe a diesel oil). Motul 300V racing oil (5W-40) I believe has around a HTHS of 4.0 or 4.1.

Once again, like I also said before, the true test would be to run a UOA after using the oil. The UOA will tell you how much your oil has sheared in service and how it is breaking down (and how your wear metals look). I have run 0W-30, 5W-30, 5W-40 and 0W-40 in my car, and the Castrol 0W-40 sheared the least amount and had the best wear numbers.

[bNks334]

Originally Posted by Iron Man

There is no 40wt oil too thick for our cars, since then they wouldn't be a 40wt by definition.

You seemed to contradict yourself on a few things. 40 is just a category of oil with a certain Kinematic*** viscosity at 210f (below the operating temp of our cars). A 40wt oil could have a Kinematic range of anywhere from cSt 12.5 to 16.3

We care about dynamic viscosity though. The dynamic viscosity of the oil (which is what changes oil pressure and heat under load) varies significantly within each category and directly correlates to shear resistance (cP).

"The viscous shear stress τ is proportional to the shear rate, the dynamic viscosity η being the proportionality factor. So, thicker oils have a higher viscosity value causing relatively higher shear stresses at the same shear rate."

You'd have to monitor oil pressure as you increase cP to verify whether or not you're doing more harm than good by using a thicker oil. I can't say I have any idea what the limit would be.

Originally Posted by Iron Man

Since LL-01 requires a 3.5 minimum, almost all Euro oils fall around 3.6-3.8, so once again (0W-40, 5W-30, etc.) with a A3/B4/LL-01/229.5 approval have very similar HTHS and similar shear resistance. If you want better shear stability, go with a racing oil (or maybe a diesel oil). Motul 300V racing oil (5W-40) I believe has around a HTHS of 4.0 or 4.1..

Again, 3.5 is the minimum shear resistance needed to meet ll-01. That doesn't mean you can just throw a 6.5cP oil in your engine because it handles load better and call it a better oil for racing. The clearance between moving parts can't get any bigger so using an oil that produces a thicker oil film does NOTHING after a certain point except cause more stress.

In regard to UOA's, not all shear occurs permanently. Modern synthetics are designed to shear under load and then return to their previous state. A UOA only tells you how much permanent damage has been done to the oil (it tells you how far the current oil is from its original spec). Increased oil pressure and heat from using an oil that is too thick will increase stress on moving parts. This wont show as additional metal on metal wear... You'll get less life out of your engine and the oil though...

But hey, we can go back and fourth all day and I am no expert in Tribology.

[Iron Man]

Originally Posted by bNks334

You seemed to contradict yourself on a few things. 40 is just a category of oil with a certain Kinematic*** viscosity at 210f (below the operating temp of our cars). A 40wt oil could have a Kinematic range of anywhere from cSt 12.5 to 16.3

We care about dynamic viscosity though. The dynamic viscosity of the oil (which is what changes oil pressure and heat under load) varies significantly within each category and directly correlates to shear resistance (cP).

"The viscous shear stress τ is proportional to the shear rate, the dynamic viscosity η being the proportionality factor. So, thicker oils have a higher viscosity value causing relatively higher shear stresses at the same shear rate."

You'd have to monitor oil pressure as you increase cP to verify whether or not you're doing more harm than good by using a thicker oil. I can't say I have any idea what the limit would be.



Again, 3.5 is the minimum shear resistance needed to meet ll-01. That doesn't mean you can just throw a 6.5cP oil in your engine because it handles load better and call it a better oil for racing. The clearance between moving parts can't get any bigger so using an oil that produces a thicker oil film does NOTHING after a certain point except cause more stress.

In regard to UOA's, not all shear occurs permanently. Modern synthetics are designed to shear under load and then return to their previous state. A UOA only tells you how much permanent damage has been done to the oil (it tells you how far the current oil is from its original spec). Increased oil pressure and heat from using an oil that is too thick will increase stress on moving parts. This wont show as additional metal on metal wear... You'll get less life out of your engine and the oil though...

But hey, we can go back and fourth all day and I am no expert in Tribology.

Like I said, I don't think we will ever agree and we can go back and forth forever. All I have to say, is that when BMW was having engine failures in one of their M-engines a few years back (bearing failures I believe), they helped solve the problem by requiring a heavy 10W-60 oil, not by requiring a 5W-30.

[bNks334]

Originally Posted by Iron Man

Like I said, I don't think we will ever agree and we can go back and forth forever. All I have to say, is that when BMW was having engine failures in one of their M-engines a few years back (bearing failures I believe), they helped solve the problem by requiring a heavy 10W-60 oil, not by requiring a 5W-30.

Maybe I am misinformed, but I read it the other way around. BMW recommended 10w60 oil in the s65. The S65 was produced with very tight bearing tolerances. People have moved to 40wt and even 30wt oils to better match the tighter engine tolerances.

Either way, Bmw now recommends any ll-01 oil for use in their M engines (that would include the 30wt and 40wt oils we are discussing). They specifically name the S65 and S54 engines that became known for eating bearings.

[Iron Man]

Originally Posted by bNks334

Maybe I am misinformed, but I read it the other way around. BMW recommended 10w60 oil in the s65. The S65 was produced with very tight bearing tolerances. People have moved to 40wt and even 30wt oils to better match the tighter engine tolerances.

Either way, Bmw now recommends any ll-01 oil for use in their M engines (that would include the 30wt and 40wt oils we are discussing). They specifically name the S65 and S54 engines that became known for eating bearings.

No, I'm talking about BMW using it for the S54, replacing 5W-30. They could not make the 5W-30 work for the engine, so I imagine engine failures would have been even worse using a 5W-30. Either way, they needed a thicker oil.

[Dackelone]

Originally Posted by bNks334

Maybe I am misinformed, but I read it the other way around. BMW recommended 10w60 oil in the s65. The S65 was produced with very tight bearing tolerances. People have moved to 40wt and even 30wt oils to better match the tighter engine tolerances.

Either way, Bmw now recommends any ll-01 oil for use in their M engines (that would include the 30wt and 40wt oils we are discussing). They specifically name the S65 and S54 engines that became known for eating bearings.

^^I think you are thinking about the e9x V8 M3 S65 engines. I also "heard" that people have switched to a thinner oil from the TWS 10w60 Castrol on the S65.

But we are talking about the N54/N55 engines.

Engine oil is like a religion... everyone think's theirs is best.

[bNks334]

Originally Posted by Dackelone

^^I think you are thinking about the e9x V8 M3 S65 engines. I also "heard" that people have switched to a thinner oil from the TWS 10w60 Castrol on the S65.

But we are talking about the N54/N55 engines.

Engine oil is like a religion... everyone think's theirs is best.

I'll run anything if it costs $10 for 5 quarts on clearance lol!