[chris719]

Originally Posted by aerobod

BMW engineered the B58 to be run on 0w20 oil, as is the case with most of their current engines. 0w30 is specified as an alternative fill if the correct 0w20 isn’t available. Using a viscosity higher than specified may lead to lower oil flow rates and localized overheating (such as in very tight tolerance journal bearings) in certain high load operating conditions.

Old technology engines with much looser tolerances would need a higher oil viscosity to maintain oil pressure at high loads due to loose tolerances.

Sorry, I have to disagree with you here, which is rare because I find I usually agree with you .

First, it’s not “tolerances”, the correct term is clearances. Tolerances are +/- allowances and say nothing about clearance. Second, there’s no evidence the industry has significantly reduced main or connecting rod clearances in the past 10 years. It’s hard to find data on a lot of engines but spot checking doesn’t show a big shift from the N engine days. Third, even if they did, there’s a lot of scaremongering on thicker oils that does not align with the actual data.

For example, Castrol’s BMW LL17FE+ 0W-20 is 43 cSt at 40 C. Mobil 1 0W-40 LL01 or PPE 5W-40 are approximately 13.8 cSt at 100 C (operating temp). The 20 grade oil at 40 C is over 3 times thicker than the 40 at 100 C. If you plot the viscosity curves out, you’ll see the 0W-20 at 40C is the same viscosity as the 0W-40 at roughly 55C. So, if the difference between the 20 and 40 were deleterious because the engines are “tight”, we’d be blowing up engines in Canada on the regular even with a 0W-20. You can plot the kinematic viscosity with several tools to get a rough idea. It’s a falling exponential function of increasing temperature. If the 5 cST or 0.8 cP HTHS difference at operating temp was a problem then these engines would be self harming during warm up cycles even with the thinnest oils.

As long as the oil has an appropriate winter rating and BMW spec I do not see operating viscosity being an issue. The thickest BMW LLXX approved oil is a 5W-50 and while I wouldn’t choose it personally, I’m sure there are people using it on the track without issues. Keep in mind that the oil pumps are positive displacement pumps and so as long as the oil is pumpable (guaranteed by W rating) it will flow. I don’t see bypass being an issue because the system should be designed to handle any SAE 0W oil which only guarantees a maximum dynamic viscosity via CCS at -35 C.

[aerobod]

Originally Posted by chris719

Sorry, I have to disagree with you here, which is rare because I find I usually agree with you .

First, it’s not “tolerances”, the correct term is clearances. Tolerances are +/- allowances and say nothing about clearance. Second, there’s no evidence the industry has significantly reduced main or connecting rod clearances in the past 10 years. It’s hard to find data on a lot of engines but spot checking doesn’t show a big shift from the N engine days. Third, even if they did, there’s a lot of scaremongering on thicker oils that does not align with the actual data.

For example, Castrol’s BMW LL17FE+ 0W-20 is 43 cSt at 40 C. Mobil 1 0W-40 LL01 or PPE 5W-40 are approximately 13.8 cSt at 100 C (operating temp). The 20 grade oil at 40 C is over 3 times thicker than the 40 at 100 C. If you plot the viscosity curves out, you’ll see the 0W-20 at 40C is the same viscosity as the 0W-40 at roughly 55C. So, if the difference between the 20 and 40 were deleterious because the engines are “tight”, we’d be blowing up engines in Canada on the regular even with a 0W-20. You can plot the kinematic viscosity with several tools to get a rough idea. It’s a falling exponential function of increasing temperature. If the 5 cST or 0.8 cP HTHS difference at operating temp was a problem then these engines would be self harming during warm up cycles even with the thinnest oils.

As long as the oil has an appropriate winter rating and BMW spec I do not see operating viscosity being an issue. The thickest BMW LLXX approved oil is a 5W-50 and while I wouldn’t choose it personally, I’m sure there are people using it on the track without issues. Keep in mind that the oil pumps are positive displacement pumps and so as long as the oil is pumpable (guaranteed by W rating) it will flow. I don’t see bypass being an issue because the system should be designed to handle any SAE 0W oil which only guarantees a maximum dynamic viscosity via CCS at -35 C.

Tolerances vs clearances may just be semantics of UK vs US engineering terminology. Tighter tolerances lead to more controlled clearances. From an engineering drawing perspective, the tolerances are specified, which will lead to a clearance range. Parts are machined to a tolerance, clearances can be matched in some cases by choosing parts that are at the same end of the tolerance range.

From an oil viscosity perspective, too high a viscosity can be problematic. One example of this is my Caterham engine that I recently rebuilt. The.stock tolerances on the main bearing housings are 57.029 +/- 0.011mm. The bearing shells (of which there are about 10 sizes) need to be matched to give between 0.019 and 0.035mm clearance for the specified 0w20 or 5w30 oils, but the motor sport clearances are advisable to be at the top end of that range when running 5w50 or 10w60 oils, otherwise flow rate and bearing cooling will be lower than anticipated when the oil is fully warm and the engine is at max revs. In contrast to a European spec engine, North American v8s are typically around 0.076mm for bearing clearances.

At 130C oil temp with my 0.035mm bearing clearances, I see 3.5bar oil pressure with 5w50 oil at maximum pump capacity and 8300RPM, but the old bearing clearances closer to 0.020mm gave the same pressure (and consequent flow rates) with a 5w30 oil.

Bottom line is matching the oil to the engine needs and component tolerances (leading to a given clearance) that are used, but too high viscosity may not give the right result if the engine is not built for that viscosity.

[chris719]

Originally Posted by aerobod

Tolerances vs clearances may just be semantics of UK vs US engineering terminology. Tighter tolerances lead to more controlled clearances. From an engineering drawing perspective, the tolerances are specified, which will lead to a clearance range. Parts are machined to a tolerance, clearances can be matched in some cases by choosing parts that are at the same end of the tolerance range.

From an oil viscosity perspective, too high a viscosity can be problematic. One example of this is my Caterham engine that I recently rebuilt. The.stock tolerances on the main bearing housings are 57.029 +/- 0.011mm. The bearing shells (of which there are about 10 sizes) need to be matched to give between 0.019 and 0.035mm clearance for the specified 0w20 or 5w30 oils, but the motor sport clearances are advisable to be at the top end of that range when running 5w50 or 10w60 oils, otherwise flow rate and bearing cooling will be lower than anticipated when the oil is fully warm and the engine is at max revs. In contrast to a European spec engine, North American v8s are typically around 0.076mm for bearing clearances.

At 130C oil temp with my 0.035mm bearing clearances, I see 3.5bar oil pressure with 5w50 oil at maximum pump capacity and 8300RPM, but the old bearing clearances closer to 0.020mm gave the same pressure (and consequent flow rates) with a 5w30 oil.

Bottom line is matching the oil to the engine needs and component tolerances (leading to a given clearance) that are used, but too high viscosity may not give the right result if the engine is not built for that viscosity.

I'll have to disagree on your definition of tolerance. It is internationally known and established in engineering. I'm an engineer, have worked with engineers on every continent, and I'm familiar with GD&T. Tolerance is allowed variation. The dictionary states:

Tolerance
The allowable deviation from a standard, especially the range of variation permitted in maintaining a specified dimension in machining a piece

Clearance
The distance by which one object clears another, or the clear space between them.

You will note that all of Mahle, King, Kolbenschmidt, etc. documentation use this terminology correctly.

[aerobod]

Originally Posted by chris719

I'll have to disagree on your definition of tolerance. It is internationally known and established in engineering. I'm an engineer, have worked with engineers on every continent, and I'm familiar with GD&T. Tolerance is allowed variation. The dictionary states:

Tolerance
The allowable deviation from a standard, especially the range of variation permitted in maintaining a specified dimension in machining a piece

Clearance
The distance by which one object clears another, or the clear space between them.

You will note that all of Mahle, King, Kolbenschmidt, etc. documentation use this terminology correctly.

But the component is machined to tolerances and accepted from a QA perspective when it is within the defined tolerances. A clearance isn’t used to create the component, but is defined by the tolerance of the combined components.

We may be sort of talking about the same thing, but I’m coming at it from the perspective of how tightly controlled the component manufacture is, which is based on the component tolerances. My background is also in engineering.

Mahle define the clearances needed, but work that back to the tolerances that create that clearance range: https://www.mahle-aftermarket.com/me...05r.pdf#page30, as they state “Let’s pick some typical manufacturing tolerances and look at the potential clearance range that results.”

Maybe I’m being too pedantic here.

[ZHP to B58]

Passed 100k miles earlier this year. Blackstone continues to show no issues.
I know some say the 0W-20 is only recommended by BMW to increase MPG, X oil is better, etc. As far as I'm concerned, I'm sticking with it.

[cooolone2]

Hahahaha

3 pages of nonsense! The old OIL argument discussion... Utterly ridiculous!

Use whatever you want, just change it often (<7k miles)

No discussion on why the B58 engine on different models has different oil recommendation? Same engine, same bearings, same except the top end?

20w oil was introduced for efficiency, ie, mileage standards... That's it! And depending upon the climate the car is located at, 30w is just fine, and for some even 40!

Personally, I run 30w oil, full synthetic, change every 5k miles regardless! Blackstone shows no issues either! If you beat on it or track it, things change, but that's another story!

What oil... Lmao! It's like asking what Underwear you prefer!