S85 oil, yeah that old question .....

[Twistee 453]

I have had a hunt through Bimmersport and for the life me I can't find a thread / raging argument on what oil to run in an S85. 

Castrol 10w60 EDGE,

Castrol 10w60 Supercar aka TWS?

BMW branded version,

Shell/BMW version,

Anything 10w60 as long as it is from a reputable brand and fully synthetic?

I think I have read more on oil opinions than anything else about S85 engines, im not looking for some cheap alternative snake oil, I'm just wondering if the attitude has changed at all towards using anything other than 10w60 Supercar?

Cheers.

[aja540i 1906]

I always use the Castrol 10w60 supercar,  but only because I wanted consistency for used oil analysis results, if you take it to BMW they will stick Shell in it, and any other 10w60 is probably going to be fine. I doubt the Warehouse have a no name 10w60!

The only advice I would offer is to not wait 25k between changes, which is what the CBS will start with after a reset.

[str8_6 275]

I use Castrol 10w60 supercar in the M5. Buy it from Supercheap when on sale. Don’t buy directly from the dealer, they charge an arm and leg for the same product. 

[GorGasm 563]

Penrite 10w60.

[BM WORLD 1283]

i have some castrol 10w-60 for sale if needed $100 for 5L

[Twistee 453]

Thanks for the input - I didn't know that Supercheap sold 10w60 Supercar, I thought they only sold EDGE as I've never seen it advertised that I can think of. @aja540i totally agree on the oil change frequency, who do you use for the oil analysis? @BM WORLD Thanks, I'll touch base in the near future and grab a couple of containers. 

[M3AN 4016]

Repco also sell the supercars stuff, I doubt SuperCheap will restock it now that their relationship with Supercars is over (they don't have it online, may be some shelf stock though).

https://www.repco.co.nz/en/oils-fluids/engine-oils-fluids/engine-oil/castrol-edge-synthetic-10w-60-engine-oil-5l-3412396/p/A1304624

But wait for it to go on special if you can, it's regularly offered for ~40% off which makes a huge difference.

But also this: "Anything 10w60 as long as it is from a reputable brand and fully synthetic?"

[KwS 2425]

Regular changes and not following the BMW super long intervals is more important than what brand 10W60 to use. Half the problem with modern car engines are due to the long intervals.

[aja540i 1906]

On 11/6/2021 at 1:58 PM, Twistee said:

Thanks for the input - I didn't know that Supercheap sold 10w60 Supercar, I thought they only sold EDGE as I've never seen it advertised that I can think of. @aja540i totally agree on the oil change frequency, who do you use for the oil analysis? @BM WORLD Thanks, I'll touch base in the near future and grab a couple of containers. 

I use Gough, they have a branch just around the road from work but all the testing is done in Christchurch I believe, you buy the kit from them and drop it back to them, they send it to the lab and email the results.

[Michael. 2313]

10 hours ago, aja540i said:

I use Gough, they have a branch just around the road from work but all the testing is done in Christchurch I believe, you buy the kit from them and drop it back to them, they send it to the lab and email the results.

I've used them over a dozen times for a variety of cars since you told me about them years ago. Super useful 

[E30 325i Rag-Top 2956]

On 11/7/2021 at 10:48 AM, M3AN said:

Repco also sell the supercars stuff, I doubt SuperCheap will restock it now that their relationship with Supercars is over (they don't have it online, may be some shelf stock though).

I think you have added an extra “s” on to the end of the name, the oil is not linked to the Aussie racing series of a similar name AFAIK.

[limepanda 13]

Figure I'll add my 2c, probably not a popular opinion around here but whatever.

10w60 is just too thick to flow properly and is likely why so many of these engines have rod bearing failures, the rod bearing and rod side clearances are tiny and not at all suited to a 60 weight, they're barely big enough for a 30 weight. 10w60 simply isn't needed, and most people will have better results with a 5w30. Benefits include more flow, less bearing issues, lower oil temps, faster air bubble release, quicker draining into the sump so less risk the pickup will suck air, HP increase due to less viscous drag and less pumping loss, among other benefits. 

[M3AN 4016]

24 minutes ago, limepanda said:

Figure I'll add my 2c, probably not a popular opinion around here but whatever.

10w60 is just too thick to flow properly and is likely why so many of these engines have rod bearing failures, the rod bearing and rod side clearances are tiny and not at all suited to a 60 weight, they're barely big enough for a 30 weight. 10w60 simply isn't needed, and most people will have better results with a 5w30. Benefits include more flow, less bearing issues, lower oil temps, faster air bubble release, quicker draining into the sump so less risk the pickup will suck air, HP increase due to less viscous drag and less pumping loss, among other benefits. 

Hmm, there's a lot to unpack there, most of it not true I'm afraid.

But we can skip the unpacking because it's my understanding that BMW themselves stipulate 10w60 for the S85 and if that's the case, that's what you should use unless you have non-typical requirements. The one exception to that is actually the cold viscosity because, at least north of Taupo, we have a very moderate climate so you could arguably go to a 25w60 if a good one were available, which is precisely the opposite of your recommendation.

Rules of thumb for modern 4-stroke engine oils:

1. Always use a high quality fully synthetic oil
2. Base the number before the w on your climate, but never lower than the manufacture's recommendation
3. Base the number after the w on how you use the car, but never lower than the manufacture's recommendation
4. The smaller the gap between the hot and cold viscosities the better (less oil pressure variance)

Of course it gets very nuanced beyond these basic rules but most people need not worry about that.

Edited December 5, 2021 by M3AN

[limepanda 13]

It's worth pointing out that in later revisions BMW increased rod bearing clearances and retroactively approved lower weight oils like 0w40 and 5w30, so they know there was an issue there.

As long as an engine can maintain adequate oil pressure (and flow) there is no real downside to running a lower viscosity oil (to a point). I would highly recommend against a 25 cold weight oil, most wear happens at startup and the quicker you can lubricate things the less damage will be done. Regardless of climate and ambient temp you should be aiming for the thinnest cold weight oil possible, because it will always be thicker when cold than when it's at operating temp (this also means less oil pressure variance). Every oil thins out as it heats up and thickens as it cools down, no matter if it is a straight weight or a multi-viscosity. For example: 0w30 is 5.6 times thicker when cold, 5w30 is 5.8 times thicker when cold, 10w30 is 6.2 times thicker when cold. Thinner oil flows more freely through all the restrictions inside an engine, oil flow is lubrication and more lubrication equals better wear protection. There is no reason to give that up, as long as you have enough oil pressure to maintain flow (65psi in this case). Oil flow and protection by a good quality engine oil are much more important than “steady oil pressure” at the highest possible numbers. Oil viscosity doesn't play a role in an oil’s wear protection capability, it's determined by its base oil and its additive package “as a whole”, with the primary emphasis on the additive package which contains the extreme pressure anti-wear components.