Thread: 5W40 on M2C
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      01-18-2020, 02:38 AM   #24
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Drives: '08 M Roadster
Join Date: Oct 2007
Location: NJ

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Originally Posted by widetyres View Post
In the UK they are setting 20k miles (32k km) intervals - way too long to go without an oil change imo.

(edit: doh! this is with n55 m2 and see you have m2c)

And they recommend/insist on 0w30, which is super light for a performance car. Good to know that they use 0w40 in DE - I'll use it when I diy change.
What viscosity you need is related to your oil temps. If you don't reach high temps then you don't really benefit from a 40 or higher. A plain bearing like a rod bearing or main bearing is lubricated by the flow of oil. Oil thins as temperature rises, and at some point the oil film is too thin to bear the load. If you are driving on the street and not moving the needle past the setpoint, then you probably don't need a thicker oil. If you track the car, sure, you might want a heavier oil. On the street where you may spend some time driving with a cold engine, it's arguable that the 0w30 could be superior depending on your driving habits. Would be nice if the cars came with a good oil pressure gauge.