5w50 in place of 10w60 for BMW M3

[sibhus]

Own an e90 series M3 with the S65 V8 which is specified for use with 10w-60. Ironically these cars are prone to rod bearing failures and based on all the occurrences, they have occurred with the 10w-60 oil. I often wonder if BMW just blew it with this weight, given the rod bearing clearances are so tight and that a thinner oil would be better. My car is purely a street car which gets at most 6k of usage a year, so I wonder if using Mobil 5w-50 would be a better alternative year round. Im in the DC area and we usually go from about 20-100F year round.

Curious about others thoughts and opinions., thanks.

 

[a2gtinut]

good point. I used to be connected with that brand. This why E46, E9x cars had this rev limiter based on engine temperature. 10w60 works fine when engine fully warmed up but in the Winter--- this is asking for trouble which many owners have experienced.
5w50 sounds much better for Winter

 

[RooflessVW]

I think M1 5W-50 would suit your car fine.

I suspect it will stay in grade longer than the 10W-60 and it carries Porsche and Mercedes approvals.

However, I don't think the rod bearing "Troubles" are something to be solved by viscosity.

 

[Cujet]

In fact, the 10W-60 oil choice was an attempt to mitigate rod bearing failures. BMW engineers know RPM based inertial loads are beyond the capabilities of lower viscosity oils. So a switch to a lower viscosity will not give a better result. However, the 10W-60 oils are not known for staying in grade properly, and the extended oil change intervals don't help that.

BMW's initial claim that bearing clearance was "too tight" is incorrect, has become a bit of internet legend, and was simply a way to attempt to address the problem. Increasing bearing clearance did NOTHING to improve the problem. The bearings are insufficient for the loads involved. Period, end of story. Higher viscosity and higher oil pressure are the only things that help a "too small" bearing live under high loads.

Also note, combustion loads are only part of the equation. Inertial loads at higher RPM far exceed combustion loads.

If the car is driven hard, the best solution seems to be preventative bearing changes at 50 or 60K miles, frequent oil changes and sufficient viscosity.

Edit to add that a gentle warm up is also a very good idea and seems to be part of the solution. Also, don't forget that cars driven gently tend not to have the bearing problems. There are plenty of examples with high miles and zero bearing issues.

Edit: For the bearings to be sufficient, they would have to be as much as 40% wider. Or reciprocating mass would have to be reduced.

 

[d00df00d]

Originally Posted by sibhus
Own an e90 series M3 with the S65 V8 which is specified for use with 10w-60. Ironically these cars are prone to rod bearing failures and based on all the occurrences, they have occurred with the 10w-60 oil. I often wonder if BMW just blew it with this weight, given the rod bearing clearances are so tight and that a thinner oil would be better. My car is purely a street car which gets at most 6k of usage a year, so I wonder if using Mobil 5w-50 would be a better alternative year round. Im in the DC area and we usually go from about 20-100F year round.

Curious about others thoughts and opinions., thanks.

Not all the "occurrences of failure" (really just pics of excessive-looking wear patterns) were on 10W-60. Someone on one of the FB groups recently reposted a pic of a set of bearings with very few miles on them, which had been run with 0W-40. Pretty sure there have been others.

While it's highly plausible that thinner oil might help, there's basically zero evidence that it actually HAS helped any S65s. Time may tell otherwise. But for now, that's where we're at.

Regarding the clearance issue and whether BMW "blew it" with 10W-60: Maybe they did. But here's something to keep in mind: Those weren't one-time things for BMW M. If they were, it'd be easier to pass them off as bad calls. But BMW doubled, tripled, and quadrupled down on those clearances long after the bearing problems became apparent, even after the industry and the aftermarket handed them a "solution" on a silver platter. 10W-60 has an even longer history with the M division, and was the viscosity of their oil of choice during the S65's development; the current BMW 10W-60 is a Shell product that BMW M ostensibly specced from the get-go. As I'm sure you know, they have no problem changing lubricants and re-speccing parts. They do both all the time. They didn't do that here.

In no way does that mean they got it all right. They've certainly made big mistakes before, and failed to fix them. But they're not incompetent, or else we wouldn't be talking about the S65 in the first place. What's more likely is that there just isn't a good way to make these bearings live longer without compromising something else -- maybe because of something else about the design, as Cujet suggested. But again, we'll see as people run other oils and/or increased-clearance bearings for a lot of miles and then start doing teardowns. That's how we'll find out whether bigger bearing clearances or thinner oil really can help the bearings live longer with no side-effects elsewhere in the engine. Until then, we shouldn't assume anyone knows the S65 better than the people who developed it.

Bottom line: You'll probably be okay on Mobil 1 5W-50. That's a heck of an oil. There's just nothing (yet) to suggest it'll work out better than BMW 10W-60 in the end.

 

[Bjornviken]

move to 10w-60 was for the oil drinking problem. BTW they put over here SHU 5w-40 in the m series.

 

[d00df00d]

Originally Posted by Bjornviken
move to 10w-60 was for the oil drinking problem.

Or the bearing problem, or the potential for extreme oil temps, or because they had a contract with Castrol and something something corporate something, or some combination thereof -- depending on whom you ask...


Originally Posted by Bjornviken
BTW they put over here SHU 5w-40 in the m series.

I mean, yeah.

You should specify where "here" is.

 

[RooflessVW]

Originally Posted by Bjornviken
move to 10w-60 was for the oil drinking problem. BTW they put over here SHU 5w-40 in the m series.

In which M series?

 

[edyvw]

Originally Posted by rooflessVW
Originally Posted by Bjornviken
move to 10w-60 was for the oil drinking problem. BTW they put over here SHU 5w-40 in the m series.

In which M series?

I think he is referring to turbo I6 and TT V8.

 

[TheMidnightNarwh]

Originally Posted by edyvw
Originally Posted by rooflessVW
Originally Posted by Bjornviken
move to 10w-60 was for the oil drinking problem. BTW they put over here SHU 5w-40 in the m series.

In which M series?

I think he is referring to turbo I6 and TT V8.


Yeah I know for sure the new BMW M4/M3 call for 0W-40 oil.

 

[1JZ_E46]

I would go a step further and run a 5W-40 that carries LL-01 approval. The bearing issues are not a viscosity issue. As mentioned above they are a design flaw that even 10W-60 did nothing to solve.

5W-50 will shear down a lot just like 10W-60 does. It's just too much of a viscosity spread (too much VII) for them to stay in grade.

 

[330indy]

use a robust PAO/POE oil
it will stay in grade
and flow/protect at temp extremes

 

[m3fan888]

In fact, the 10W-60 oil choice was an attempt to mitigate rod bearing failures. BMW engineers know RPM based inertial loads are beyond the capabilities of lower viscosity oils. So a switch to a lower viscosity will not give a better result. However, the 10W-60 oils are not known for staying in grade properly, and the extended oil change intervals don't help that.

BMW's initial claim that bearing clearance was "too tight" is incorrect, has become a bit of internet legend, and was simply a way to attempt to address the problem. Increasing bearing clearance did NOTHING to improve the problem. The bearings are insufficient for the loads involved. Period, end of story. Higher viscosity and higher oil pressure are the only things that help a "too small" bearing live under high loads.

Also note, combustion loads are only part of the equation. Inertial loads at higher RPM far exceed combustion loads.

If the car is driven hard, the best solution seems to be preventative bearing changes at 50 or 60K miles, frequent oil changes and sufficient viscosity.

Edit to add that a gentle warm up is also a very good idea and seems to be part of the solution. Also, don't forget that cars driven gently tend not to have the bearing problems. There are plenty of examples with high miles and zero bearing issues.

Edit: For the bearings to be sufficient, they would have to be as much as 40% wider. Or reciprocating mass would have to be reduced.

Been very careful to really keep the car at 210 before I even rev it to 4k.. and even then...I keep my revs to 4k and below..I know im too granny..

 

[Jimmy_Russells]

You have an M3 you never take over 4k?

Normally I would say follow manufacturer guidelines but 60 grade in these cars makes no sense on the street, especially when you add in all the rod bearing issues because the M dept forgot how to build engines or something. I wish they would come out and specify why they recommend that. Even if the car is tracked there are countless other cars that are also tracked on 40 grade with no issues, so either the 60 is immense overkill for track or they're using it to bandaid something.

 

[CBODY67]

BMW has spec'd 10W60 in some of their engines for decades. Back when only AZone carried that viscosity, other than BMW dealers (when it was common knowledge that BMW came from Castrol, back in the 1990s). One of BMW's "good moves" was their full-maintenance factory warranty, which meant the dealer did the oil changes and the engines got the correct oil in them. Bearing width can be a function of total engine length, by observation. Most bearing clearances are related to a certain clearance spec related to the diameter of the bearing. Bearing materials can be a compromise, though.

Just some thoughts

 

[edyvw]

You have an M3 you never take over 4k?

Normally I would say follow manufacturer guidelines but 60 grade in these cars makes no sense on the street, especially when you add in all the rod bearing issues because the M dept forgot how to build engines or something. I wish they would come out and specify why they recommend that. Even if the car is tracked there are countless other cars that are also tracked on 40 grade with no issues, so either the 60 is immense overkill for track or they're using it to bandaid something.

Something went wrong here with design. Rod bearing in S65 have tight tolerances and XW50 should be maximum. However, BMW from get go went with 10W60. There are numerous topics on this subject and a lot of people run 5W50 Redline successfully in this engine. But, from everything so far, it seems that cold starts and lead foot while cold is major culprit.

 

[edyvw]

BMW has spec'd 10W60 in some of their engines for decades. Back when only AZone carried that viscosity, other than BMW dealers (when it was common knowledge that BMW came from Castrol, back in the 1990s). One of BMW's "good moves" was their full-maintenance factory warranty, which meant the dealer did the oil changes and the engines got the correct oil in them. Bearing width can be a function of total engine length, by observation. Most bearing clearances are related to a certain clearance spec related to the diameter of the bearing. Bearing materials can be a compromise, though.

Just some thoughts

Bearing tolerances on S65 are pretty tight. Something else went south here.

 

[BMWTurboDzl]

Word from Munchen is that because the S65/S85 are based on the P84 Formula 1 engine BMW expected owners to replace the bearings every year or two.

 

[d00df00d]

Word from Munchen is that because the S65/S85 are based on the P84 Formula 1 engine BMW expected owners to replace the bearings every year or two.

(because it smells incorrect to me)

 

[BMWTurboDzl]

View attachment 53951

(because it smells incorrect to me)

ROFL... which part? We do know that these engines are based off the P84, and how many races did F1 require that an engine last prior to being rebuilt? 2 races or the season? Obviously I'm being a little tongue-n-cheek but a tiny part of me thinks the bearing issues are related to the design carryover from the P84.