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#1069140 - 01/21/08 01:45 AM Why does the BMW M3 use 10W-60?
rearviewmirror Offline


Registered: 12/19/06
Posts: 72
Loc: Austin TX
I've always wondered why my M3 uses such a heavy oil. It's the S54 3.2l inline 6. I just can't figure out why the car would run such a heavy oil, especially in today's fuel conserving world. I reckon that BMW must have really gone after volume vs pressure regardless of engine temp. They are strict on the amount of revs used while the engine is warming, the tach slowly turns off red lights raising the redline as the engine warms.

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#1069146 - 01/21/08 02:05 AM Re: Why does the BMW M3 use 10W-60? [Re: rearviewmirror]
double vanos Offline


Registered: 08/05/04
Posts: 983
Loc: Houston, Texas
I don't think that BMW is worried so much about conserving fuel as they are trying to conserve the rod bearings in that engine.

IIRC that engine has an 8000 rpm redline. I'm sure that in the middle of that 8000 rpm there is quite of long crankshaft crazy harmonics going on so maybe BMW hopes to dampen all that with a thicker oil.

Also that engine has a lot of highly stressed chains inside and maybe BMW figures that by the time their nutty 15000 mile oil changes come due the 10w60 oil has sheared and cooked down to a 5w20.

Amazes me that Honda can produce engines that dwell at those lofty RPM's and they require ordinary street oil - not the exotic Castrol TWS oil. Go figure. Cheers!
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#1069175 - 01/21/08 06:00 AM Re: Why does the BMW M3 use 10W-60? [Re: double vanos]
Pablo Offline


Registered: 10/28/02
Posts: 46687
Loc: Duvall WA - Pacific NW USA
I thought it was because of some piston ring issues??

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#1069177 - 01/21/08 06:27 AM Re: Why does the BMW M3 use 10W-60? [Re: Pablo]
moribundman Offline


Registered: 06/02/03
Posts: 23591
The early S54 engines had problems with rod bearings. Actually, problems with rod bearings (and cams) aren't anything new in case of BMWs. Not aware of any ring issues...

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#1069178 - 01/21/08 06:37 AM Re: Why does the BMW M3 use 10W-60? [Re: moribundman]
moribundman Offline


Registered: 06/02/03
Posts: 23591
Also, the S54 engine has very small rod bearing clearances. Because of the relatively long stroke, piston speed is considerably higher than it is in some other BMW engines. I suppose 10W-60 offers a necessary safety margin.

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#1069180 - 01/21/08 06:46 AM Re: Why does the BMW M3 use 10W-60? [Re: moribundman]
moribundman Offline


Registered: 06/02/03
Posts: 23591
Another thing: as far as I know, the S54 engine was outsourced to a BMW engine assembly plant in Steyr (Austria), and only "core parts" (per BMW) of the engine were actually fabricated by BMW. I guess it's possible that rod bearings weren't considered "core parts" and bought from who-knows-where.

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#1069181 - 01/21/08 06:49 AM Re: Why does the BMW M3 use 10W-60? [Re: moribundman]
vacuum_6 Offline


Registered: 12/14/07
Posts: 56
Loc: Illinois
A buddy of mine bought a 20xx M6. A liter of WXX60 is $35.00 He's burning a liter every 750 miles, the dealer told him that's normal. I told him thatís excessive.
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#1069213 - 01/21/08 08:17 AM Re: Why does the BMW M3 use 10W-60? [Re: vacuum_6]
rearviewmirror Offline


Registered: 12/19/06
Posts: 72
Loc: Austin TX
It's just surprising to me, the M54 engine in the 330Ci uses 5W-30. I have no doubts it's due to tolerances, the S54 is a very precise engine, and other than the rod bearing recalls on early motor they're quite solid. They are at the max of their performance range, any mods is like setting a ticking timebomb. 100+HP per liter is a good bench market, but now lots of cars are achieving this, and without heavy oil. :)

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#1069214 - 01/21/08 08:19 AM Re: Why does the BMW M3 use 10W-60? [Re: moribundman]
Pablo Offline


Registered: 10/28/02
Posts: 46687
Loc: Duvall WA - Pacific NW USA
Thanks mori! I think I mixed this up with some northern German auto manufacturer and wrong/mis-installed rings....... .....my memory is going!

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#1069215 - 01/21/08 08:23 AM Re: Why does the BMW M3 use 10W-60? [Re: vacuum_6]
d00df00d Online   content


Registered: 10/20/05
Posts: 9218
Loc: PA
Relatively long stroke is right -- it's a 3.2L 6cyl, and it's undersquare.


As far as I know:

- The rod bearings (and other bearings) see [censored] because of the astronomical piston speeds.
- The Double VANOS system needs huge oil pressures.
- The piston rings are designed for the lowest possible friction, which means high clearances.
- BMW needed a way to minimize the chance that customers will buy whatever oil they see on the shelf.

Hence, an exotic oil in an exotic (and high) viscosity.


The E46 M3 did have rod bearing issues in the beginning, but that was due to manufacturing issues. The recommended oil was changed from BMW's 5w-30 to Castrol TWS 10w-60 about halfway through 2001, which did not coincide with BMW's acknowledgement and remediation of the issue.

I doubt BMW would source something as important as a rod bearing for an M3 from somewhere else unless it still met incredibly rigid standards (defects notwithstanding).

The E39 M5 was the car with the piston ring issue, but it wasn't really a problem. It just switched to a newer piston ring design after 03/2000 to permit the use of 5w-30 instead of 10w-60.

The high oil consumption in M engines comes largely from "loose" piston rings, which have to be used to minimize friction. BMW seems to have a pretty generous range of what's "normal"; I'm told that anything from zero to one quart per 1,000 miles is normal for my car (E36 M3), and its engine isn't even one of the newer exotic ones with stratospheric redlines. When you look at a new M5 or M6, remember that they have big engines AND big cylinder counts AND huge redlines, AND they are mated to quick-shifting SMG systems that need them to be able to rev like tiny engines for rev matching during shifts. That combination pretty much guarantees high oil consumption.

Honda engines are small displacement 4-cylinder engines, and they tend to use internal dimensions that are a little more sane. They can make similar specific outputs, but they just don't have as much going on inside them as BMW engines do. That's why they can get away with using more down-to-earth oils.


Again, AFAIK, FWIW, and all that good stuff.
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#1069226 - 01/21/08 08:45 AM Re: Why does the BMW M3 use 10W-60? [Re: d00df00d]
vacuum_6 Offline


Registered: 12/14/07
Posts: 56
Loc: Illinois
 Originally Posted By: d00df00d
The high oil consumption in M engines comes largely from "loose" piston rings, which have to be used to minimize friction. BMW seems to have a pretty generous range of what's "normal"; I'm told that anything from zero to one quart per 1,000 miles is normal for my car (E36 M3), and its engine isn't even one of the newer exotic ones with stratospheric redlines. When you look at a new M5 or M6, remember that they have big engines AND big cylinder counts AND huge redlines, AND they are mated to quick-shifting SMG systems that need them to be able to rev like tiny engines for rev matching during shifts. That combination pretty much guarantees high oil consumption.


Yeah but arenít the M6s a V10 5.0L?
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1987 Buick Turbo T

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#1069228 - 01/21/08 08:45 AM Re: Why does the BMW M3 use 10W-60? [Re: d00df00d]
Pablo Offline


Registered: 10/28/02
Posts: 46687
Loc: Duvall WA - Pacific NW USA
d00df00d - good post! Thanks.

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#1069258 - 01/21/08 09:23 AM Re: Why does the BMW M3 use 10W-60? [Re: Pablo]
G-MAN Offline


Registered: 11/15/02
Posts: 8869
Loc: SC
Doesn't the new M3 have a V8? And isn't 10w60 still spec'd in all the M cars, the M3 (V8) and the M5 and M6 (V10s)?

BTW, I met a guy a couple weeks ago who had a new M6. We were standing beside it talking and he left it running. Exhaust note at idle was unpleasantly loud, and I really didn't like the sound of that V10 at all. Too "UPS truck" sounding to me.
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#1069288 - 01/21/08 09:50 AM Re: Why does the BMW M3 use 10W-60? [Re: d00df00d]
SpitfireS Offline


Registered: 03/21/06
Posts: 285
Loc: the Netherlands
 Originally Posted By: d00df00d
The high oil consumption in M engines comes largely from "loose" piston rings, which have to be used to minimize friction.

Honda engines are small displacement 4-cylinder engines, and they tend to use internal dimensions that are a little more sane. They can make similar specific outputs, but they just don't have as much going on inside them as BMW engines do. That's why they can get away with using more down-to-earth oils.

Honda uses the FRM cylinder walls to reduce friction.
FRM = Fibre Reinforced Metal.
@ 9000 rpm there is a lot going on in my F20C2, 2.0l four cylinder S2000 engine.
Still, Honda recommends a 10W-30 (dino) oil.
Specific output for the F20C2 = 120hp/liter.
Designed in 1998/1999.


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#1069375 - 01/21/08 12:14 PM Re: Why does the BMW M3 use 10W-60? [Re: rearviewmirror]
pev223 Offline


Registered: 10/22/07
Posts: 32
Loc: Palm Beach, FL
It is the engine design itself is what will ultimately determine what oil you will need. Bearing clearances in particular will determine what oil pump and oil weight you will need to protect that engine. Pistons, rings etc. do not affect your oil pressure.

High performance street cars have almost always had "looser" rod and main bearing clearances.It is difficult to maintain steady oil pressure in "loose" bearings. Under normal driving conditions your oil temp will probably be around 200 degrees or so, but do some WOT driving and those oil temps will quickly rise. If that temp goes to 250 degrees your oil pump won't be able to maintain enough pressure with a light weight oil to prevent engine damage. Minimum safe rule of thumb is a minimum of 10lbs of oil pressure for every 1,000 rpm. In your car that means about 90 lbs at max rpm with "hot" oil.

If you see an engine that needs thicker oil rest assured the bearing clearances are looser than the "stock" equivalent. For example Ford is known for requiring 5w-20 oils in most of its cars. Yet the Ford GT and Shelby GT500 both come from the factory with 5w-50 oil, and it is the only reccomended oil for those cars.

As far as the oil consumption goes, low tension rings may account for some of it but it still seems high to me for a six cylinder. We have a 2006 330 i with the 255 horse power version of your engine. Oil consumption is 1 qt. per 10,000 miles. This is with 5w-30 oil.
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