It's a toughie. There are countless examples of the S54 engines going to >150k miles on the original shells. I'm not sure anybody has really pinned the problem down sufficiently enough to say if it was a manufacturing defect / batch problem or oil / service related. Perhaps it's down to number of cold starts or maybe the number of short drives where the car runs rich and additional petroleum vapour gets into the oil and changes the viscosity substantially.
Incidently Mr Vanos wrote an interesting piece on bearing shell failures (albeit on the V8 M):
https://www.facebook.com/MrVanos/posts/925018294267445
"After some questions around the S85 V10 and S65 V8 engines that seem to suffering more and more bearing failure, I've wrote a little bit of information with our take on it. This is purely our view and how we see it. We don't expect people to follow this and everyone has their own opinion.
Bearings were changed mainly due to new laws regarding copper. Now aluminium with tin coating. Some people say copper is better due to it being softer and can take oil contamination better. There isn't much oil debris these days due to clean engines and very good filtration.
Bearing shells produced in steel and lined with aluminum/tin or aluminum/tin/silicon have extremely effective anti-friction properties combined with high wear strength and exceptional resistance to corrosion. The fairly soft tin provides good conformability of the bearing to the crankshaft and is an excellent surface for embedment of dirt particles occurring as wear debris and primary dirt in the engine oil. Silicon, as an alloying element in aluminum bearings, is necessary when using cast iron crankshafts, especially “soft” shafts. The silicon smoothes the crankshaft surface to overcome any folded and smeared metal that might be covering up carbon inclusion.
Tin bearings work like Alusil blocks in that they need to have the silicone content brought out to bed in the piston rings. Same thing with the cranks, they bed in with the cranks, which copper based bearings will never do. This is good for bearing replacement as it will clean up the crank if there is any 'damage/light marking' from the original bearings contacting the crank. If a bearing has spun then it's to late and a new crank is the only option. The cranks are far to soft and a lot of material is taken off them when a bearing spins. There is no one in the uk who will warranty any repair work, ie. weld crank and regrind. I believe it can be done in the US, but i wouldn't want to warranty an engine with this done.
That being said the original bearings aren't the issue, never have been. The clearance is too tight for the oil thickness. It's that simple, 10w60 should never have been put in the engine, full stop. Nothing to do with temps either as the F10 uses 0w30/40 with 2 turbos and way higher engine temps that the S65/85 without issue, and bigger clearances on the rods. The thinner oil flows faster when cold, so the engine warms up quicker, and flows faster generally so the engine temps are slightly lower due to increase heat dissipation due to faster flow. Also, the original rod bolts are also 100% fine with no known issues, yes ARP's are stronger, but for normal use they don't fail and I've never heard off one failing. A supercharged E92 M3 or V10 would be a good idea to use ARP with the extra stress created but again it's not essential. A couple of supercharged M3s we built are running standard internals for the last 6 years now and one has covered 50k miles, no issue at all and perfect oil when it's changed. Uses Motul 300v 5w40 changed every 4K miles, has been tracked hard as well.
Common misconception is the thicker oil is better for higher temps, mobil 1 0w40 is rated to 150 degrees. If your engine sees oil temps that high the oil is the least of its worries . The safety cutoff is 125 on S65/S85. Above that it goes into limp mode. Some supercharged M3's have issues with high oil temps on track.
The 10w60 oil is like treacle when it's cold, combine this with not warming engine properly, 19000 mile oil changes, when the Castrol oil has been proven to break down after 5-7k miles and it's never going to end well.
However, an engine that's had regular oil (5-6k miles) changes, warmed up properly will be fine for big miles.
I've done a couple of rod bearing jobs on high mileage, 'over' maintained cars and they have been as new. My last V10 had 80k on it and 11 oil changes in the book. They were like new when I changed them.
Had to rebuild several very low mileage engines, less than 30k and only 2/3/4 oil changes in 10 years and engines are wrecked.
My recommendation is 5w40 race oil, Motul 300v, change every 5-6k mile and not worry about it. Use BMW bearings when changing, they are the only bearings on sale with a 2 year parts failure warranty.
All our rebuilds have to use 5w40 Motul as the oil for warranty. My own cars run Motul 300v as do all race bikes."
