[Tom M]

Thought the following message quoted from another M5 board would be of interest in case this was news to others:

"I took our new M5 in for its 1200-mile service. The service advisor called and let me know that, for 3/00 production and later E39 M5s (and Z8s (-: ), the piston rings have been redesigned to permit the use of 5W-30.
As you can imagine, I was quite surprised by this, so I asked to see the service bulletin. The bulletin is number 11 08 98 as revised in June 2000.

The exact quote is:

'M5 (S62 Engine) produced from 3/00 and all Z8s
The S62 engine incorporates redesigned piston
rings from 3/00 which permit the use of BMW
High-Performance Synthetic Engine Oil 5W-30'

The bulletin continues to emphasize that earlier M5s require the Castrol 10W-60, "to avoid engine damage". It says that it's OK to top up with lower-viscosity oils, but only if the 10W-60 is not available, and that oil consumption will increase if you do so."

 

[Stanley]

Tom...very interesting...with my M5 built 4/00, this explains why at 2500 miles, Im not down a drop of oil..thanks

 

[MEnthusiast]

how do you tell when your car was built?
ME

 

[Tom M]

ME,

I would assume your dealer could tell you. Otherwise, a rough estimate would be 4-6 weeks before you took delivery. Got mine the beginning of this month, so it was probably built mid to late May.

 

[Stanley]

ME...open the drivers door and look at the stickers posted on the pillar...one is for tire pressure..another has the vin and month and year the car was built

 

[MJ]

You can tell the manufacture month of your car by checking the sticker inside the drivers side door frame. For example mine reads 10/99.

 

[JEM]

I think the issue here isn't so much that 10W-60 or 10W-40 is superior to 5W-30 (more below) but that BMW apparently respecced the piston rings to lower oil consumption.

My car was built 3/00...I'll have to go read that TSB carefully to make sure it applies.

Now, back to the oil-viscosity issue: engine builders generally like to use the lowest-viscosity oil they can get away with, because it means lower internal friction. Historically, severe use meant thicker oil, but as long as engine temperatures and clearances are under control, this shouldn't matter too much.

 

[Tom M]

Stanley and MJ,

Thanks for the tip about the diver door sticker. I'd seen the tire pressure one but overlooked the manufacturing info one. Mine says 6/00, and I had been guessing mid to late May production, so it didn't take as long to get to me as I thought.

 

[MEnthusiast]

Yes thank you all for the tip!

ME

 

[bobafett]

sorry for being illiterate about the subject, but is 5w-40 better than the 10w-60? why / why not?

--Dan

 

[rsteele]

I seem to remember having read on this message board that the M5 engines lack piston rings. Instead, the M5's pistons make direct contact with cylinder walls, which are grooved to allow the movement of oil between the piston and cylinder. The M5's greater oil consumption was explained on that basis. Now I'm reading that the M5's "rings" have been redesigned to reduce oil consumption.

Can someone clear up my confusion? Thanks.

Richard

 

[MES]

Hopefully someone involved in the original discussion will clear this up for you, but I'll make a guess in the meantime. If the original discussion referenced not using rings, I would assume they meant not using oil rings in addition to the compression rings. There are two uses of rings (often separate)in traditional engine designs. I would be extremely surprised if there were no (compression) rings.

 

[TD]

While at the Spartanburg M5 Driving Experience they showed us a partly assembled "tech training" M5 engine. The spare piston we saw had three rings, I recall a claim that they were thinner than usual. That along with a short piston skirt - a racing engine design - is what I recall as the reason for the initial oil consumption.

They said nothing about using anything but the 10-60. A repeted point was that the recommended oil had "molecules all of the same size" and thus had super extended lubricating properties, i.e. does not break down, over other less refined oil. Simple ligic suggests that mixing another oil could undermine that thesis. Are the 5-30 molecules the same size?

I don't know for sure, maybe it is to justify the price, but it sounds reasonable to me. Me, I would hesitate to mix.

May 00 production, 1800 mi and down about 3/4 of a quart, none added yet. Usage has increased with city driving. Brought a case of the Castrol home with me.

Terry