Quote:
Originally Posted by elp_jc
I was told that by an actual owner that 10/60 was spec'ed mainly to mitigate oil consumption, but also for the bearing issue. Based on your input, that might not be correct, and since I was never interested on a 6-cyl M3, never bothered to research the issue myself. I'd be nice to know what was spec'ed at the beginning of the S54's life, when 10/60 was first spec'ed, and with which oil the oil consumption and bearing issues took place. Wrong board, but if somebody knows it'd be nice to set the record straight  .
What I want to know is why 10/60 when all other street cars I know about use 5/40 at the most. The logic behind thinner oils is it's better to pump oil faster than slower, and it makes sense. Thinner oil requires tighter tolerances as well. So what's the story with the S65 requiring a honey-like 10/60  ? |
The E46M3 with the S54 originally arrived in North America with BMW 5w-30 oil in it. BMW started having bearing problems and switched to the 10w-60 oil, but in the end there was never a correlation between oil viscosity and failures. The failures were manufacturing defects, pure and simple. The viscosity change was permanent however, regardless of whether it was necessary.
As for the viscosity difference, think of it this way - the difference between BMW 5w-30 and TWS 10w-60 in a warmed-up engine is about 15 degrees celsius. TWS shears down to a 50 weight after a few hundred miles of use and stays there. At 115 degrees Celsius, TWS has the same viscosity as 5w-30 at 100 degrees celsius.
That's the oil temperature difference between driving to work and roaring down a straight at full throttle. A regular engine in commuting service sees the same viscosity as an M engine on a track at full power.