Consensus on Oil weight

[shimmy23]

I still don't fully understand why anyone would use anything other than 10W-60.

[New2Roundel]

I realize that everyone can and should do what makes them sleep better at night, but I never understood why anyone would go with a thinner oil in a high performance engine. I could understand going a little thicker (generally speaking) for a car that sees the track. But even for just street driving, there's no objective reason to go thinner. Most times that's done, it's strictly for economy (or in drag racing). I was taken a bit back when the oil for my coyote-powered mustang specificied 5-w20 oil. Though, I believe the recommendation for track use for that engine is the addition of an oil cooler and x-w50.

In the end, I'd prefer not to mess with something where there isn't a clear reason to mess with it.

[1MOREMOD]

I've weighed all different varieties of oil and they all seem the same

[pbonsalb]

High revving high performance motors don’t necessarily need thick oil. Audi R8 and similar motor Lamborghini specify 5W30 to 5W40 (although after about 2012 the spec changes to 10W60). Porsche GT3 uses 0W40 or 5W40.

BMW was doing mass production with the E46M3, E39M5, E60M5 and E90M3 and could help the sale of what would otherwise be a low volume Castrol 10W60 and Castrol probably paid BMW to specify the oil. I don’t believe any of those cars actually require 10W60 for street use.

[dparm]

Originally Posted by pbonsalb

I don’t believe any of those cars actually require 10W60 for street use.

Then why would BMW make 10w60 the only acceptable viscosity?

This is dangerous speculation. BMW did not pick TWS mainly for marketing or budgetary reasons, though those types of factors certainly do play into the decision. Something as unusual as 10w60 has disadvantages over 5w40 that many other similar performance cars use, to your point. But those cars don't have an S65 motor, so why are we comparing them?

Unfortunately, all we can do is speculate, but if people choose to ignore the manufacturer's specifications then it's on them when things go wrong.

[pbonsalb]

Most people are most comfortable following the manufacturer’s directions. That does not mean the directions are always the best or the only way.

I don’t think the S65 is any more special than the Audi, Lamborghini and Porsche motors that run the same rpm with similar or greater output per liter and that don’t really operate differently in any significant way. Are you suggesting their clearances are even tighter than those in the already very tight S65 so they need a thinner oil? I just don’t see any real reason for the 10W60 on the street, where 99% of the E9xM3 spend their lives (and many of those spend little time on the street and mostly are in the garage).

[Obioban]

Originally Posted by pbonsalb

This is from Doug Hilary:

"Hi,
gatofast - This from BMW USA;

"*The following is the only recommended and approved synthetic oil for BMW M (Motorsport)
vehicles in the US market with gasoline engines, at the present time.

BMW Long-life rating LL-01 Synthetic Oils for BMW M vehicles
equipped with S54, S62, S65 or S85 engines

Castrol EDGE Professional TWS Motorsport SAE 10W-60 Synthetic Engine Oil,
BMW part number 07 51 0 009 420

or

Castrol Edge Professional OE 5W30 Synthetic Engine Oil
BMW part number 07 51 0 037 195"

Noting the above and the specifications LL01 of M1 0W-40 I would not hesitate to use it in a S65 engine for "everyday" use. Of course everyday use does NOT include track time or "hoon" type driving.
_________________________
Regards
Doug"

Post #3501542 - 10/03/14 08:56 PM, found in this Bobistheoilguy thread that you participated in:

https://bobistheoilguy.com/forums/ub...10W60_thing???!!!

M1 0w-40 lost LL01 certification when the reformulated it.

[sibhusz06]

What led me to start this topic was after reading this passage on BE bearings website which suggests the 10w-60 is to thick and they suggest a 5w-40 on one of their pages:

Why do the motors Blow with rod bearing failure?
BMW designed the S65 and S85 with approximately half the industry standard oil clearance. This is a trendy move among some auto manufacturers to increase gas mileage and increase horsepower. But when they do it, like in the Toyota Prius, the auto manufacturer also specifies a very thin oil to match the very small oil clearance. BMW dropped the ball here and is using very small oil clearance and very thick 10W60 oil. Many consider this its own recipe for disaster. But here's what is believed to be happening in the S65 and S85 engines.

Engines with clearance too small, couple with oil too thick, leads to premature rod-bearing related engine failures. With clearance too small and oil too thick, the lubrication around the bearing is marginal. Some metal-to-metal contact is made between the bearings and rod journal. The oil and rod bearings overheat. Some bearings seize on the crankshaft, while others will "spin" and cause a crankshaft failure. Here's the recipe how it can happen.

https://www.bebearings.com/Overview.html

[M43S7RO]

I agree that BMW got it wrong with the bearings, either in regard to clearance or specing too thick an oil for the clearance. Either way, coming out and telling people to use a thinner oil is admission that they screwed up and puts them on the hook for a lot so that's not going to happen. Add to this TAs, evaporators and leaking DCTs (this may be a Getrag issue).

Generally, I agree that oem spec is best but in that case why do we bothering changing our trans fluids and coolant if the all knowing engineers have said they are lifetime fills. In regard to these, nobody that I've seen is on board with the BMW recommendation. Do people that absolutely believe BMW is always right also not maintain these other items because BMW says? Do they change oil at 15k interval?

I do my own maintenance where I can and have always do so on my other cars. My understanding has always been that there is a range or weights that can be used for oil based on local climate and vehicle usage. The S65 is not that special in that it must absolutely not deviate from one specific weight.

From the few years I've spent on the board, I've come to my own conclusion that I need thinner cold start oil while keeping HTHSV similar to the oem when warm.

[Dr. Dre]

Originally Posted by sibhusz06

What led me to start this topic was after reading this passage on BE bearings website which suggests the 10w-60 is to thick and they suggest a 5w-40 on one of their pages:

Why do the motors Blow with rod bearing failure?
BMW designed the S65 and S85 with approximately half the industry standard oil clearance. This is a trendy move among some auto manufacturers to increase gas mileage and increase horsepower. But when they do it, like in the Toyota Prius, the auto manufacturer also specifies a very thin oil to match the very small oil clearance. BMW dropped the ball here and is using very small oil clearance and very thick 10W60 oil. Many consider this its own recipe for disaster. But here's what is believed to be happening in the S65 and S85 engines.

Engines with clearance too small, couple with oil too thick, leads to premature rod-bearing related engine failures. With clearance too small and oil too thick, the lubrication around the bearing is marginal. Some metal-to-metal contact is made between the bearings and rod journal. The oil and rod bearings overheat. Some bearings seize on the crankshaft, while others will "spin" and cause a crankshaft failure. Here's the recipe how it can happen.

https://www.bebearings.com/Overview.html

I had my bearing replaced with VAC bearings. They have more clearance. I realize that the majority of the wear probably occurs during start up. However, I make sure the oil is up to temp before any hard driving. Run whatever you want. It's your car.

[pbonsalb]

I might run 10W60 after I change my rod bearings again to added clearance bearings (which were not yet available when I first changed mine). But the main bearings are apparently tight clearance also, and there are no added clearance bearings for the crank. Nowhere near as many crank bearing related engine failures, though.