What oil?

[digger]

every time someone brings up engineers I always think about their structural or mechanical ones who developed our RACP, exhaust hub tabs, and rod bearing (early pre LCI cars, and of course BMW blamed manufacturing, which may have been true). There is engineering and then there is engineering within the corporate arena and sometimes, well..... lol.

My sentiments exactly.

[IamFODI]

I don't care about oil and I'm dumb so I just use 10w-60, but I will say every time someone brings up engineers I always think about their structural or mechanical ones who developed our RACP, exhaust hub tabs, and rod bearing (early pre LCI cars, and of course BMW blamed manufacturing, which may have been true). There is engineering and then there is engineering within the corporate arena and sometimes, well..... lol.

Very true.

Could you explain how this maps onto the oil discussion? Are you saying BMW's recommendations aren't worth more than the aftermarket's (or our own opinions) because their engineering was obviously compromised by cost-cutting?

[oceansize]

Very true.

Could you explain how this maps onto the oil discussion? Are you saying BMW's recommendations aren't worth more than the aftermarket's (or our own opinions) because their engineering was obviously compromised by cost-cutting?

Can't, not qualified to talk about oil at any meaningful level. Not even the least little bit. See bottle, open bottle, pour contents of bottle in little hole.

[bhoom_S54]

I used Motul 10w60 here In Oregon. Works for me

[BL92]

Well i ended up throwing in the towel today, I found NOS Castrol Supercar 10w60 ( old label ) at an auto parts store, 15 minutes south from where i live, Bottles are date stamped 2023, Made in Germany

[0-60motorsports]

Well i ended up throwing in the towel today, I found NOS Castrol Supercar 10w60 ( old label ) at an auto parts store, 15 minutes south from where i live, Bottles are date stamped 2023, Made in Germany

Nice! I just buy them from Audi in FL whenever im over in the USA LOL.

[Slideways]

Sounds familiar

[dHam_Slow.46M]

Sounds familiar

So you're saying I should just stock pile 10W60 and use it on all my vehicles... GOT IT!

[chris719]

More salt on the wounds, Sorry guys lol


My ACL STD, measured at .002



Here are some recommended rod bearing oil clearances for various oil viscosities:

.0015 to .0018 for 5W-20 or 20W

.002 to .0024 for 5W-30 or 30W

.0025 to .0029 for 10W-40 or 40W

.0030 to .004 for 20W-50 or 50W

.0041 to .005 for 10W-60 or 60W



Video below

You have to understand this is a rule of thumb. It would also be better to say these are the MINIMUM or "recommended" viscosities for those clearances also. As you can see if you read SAE journal articles or more authoritative sources with data, having a thicker oil with a clearance of 0.002 is not a problem, in fact it still has benefits especially at low RPM / high load situations. The only issue is that you are getting into diminishing returns and at some point you just start having unnecessary frictional losses with no benefit to preserving hydrodynamic operation. Bottom line though, if you have a design with rod bearing issues, going to a thinner oil is not going to solve your problem; it doesn't mean the thicker oil will always help you, but it won't hurt. If you look at the data from Dr. Dmitri Kopeliovich, a 10W-60 does indeed still increase the MOFT over a 30 or 20 even at a tiny 0.0004" bearing clearance.

https://www.substech.com/dokuwiki/doku.php?id=oil_clearance_and_engine_bearings

I feel confident in saying that while the 10W-60 does not solve the BMW rod bearing issues, it does not contribute and would be marginally worse if they used the standard LL-01/LL-04 oils. Personally, I would not use any oil with HTHS lower than 5.0 cP on S54.

[JakeM346]

So you're saying I should just stock pile 10W60 and use it on all my vehicles... GOT IT!

Use 10w60 cold on an engine designed for 0w20…….something is gonna break….at some point….just saying😂
no but for real why trade the cold start disadvantages for diminishing returns.+ increased pumping loses
the main reason for choosing 10w60 is temperature resistance.
all the old Porsche engine run it and the s54 because these engine can get ….really really hot
also why they have oil coolers

[chris719]

Yeah, the main problem is we don't have real data on lower viscosity oils, and S54 doesn't exactly have the best oil pressure as it is. It's hard to form a logical argument for a lower HTHS oil. It really depends if one believes the wear is from either cold start, low RPM / high load operation, or high RPM operation.

I think a 5W-50 could be a good winter oil, but we have to be careful in selection. The 10W-60 has a lot of VII polymer but the base oil is still pretty robust if it's a modern synthetic 10W. A 5W-50 will have similar amounts of VII but the worst-case base viscosity it could potentially shear to, the "HTFS" in BITOG language, will be lower than the 10W-60. Since S54 clearly does not maintain hydrodynamic lubrication at all times we have to assume mixed/boundary contact and the shear rates could go way up. Most 5W-50s like Mobil 1 FS X2 are relatively thin also with HTHS < 4.5 and seem to not hold viscosity that well. The only two that look good are the Red Line 5W-50 which has close-enough KV100 and HTHS to Castrol 10W-60, and Motul 300V 5W-50 which is thinner kinematically but has 5.0 HTHS like the Red Line.

If we assume higher HTHS is more protective, which is likely but unproven, then the updated Ravenol RSS 10W-60 is probably what everyone should run. Crazy HTHS (6.4) vs KV100 on that one.