Another Quart of Oil Requested - 2005 Mercedes-Benz CL65 AMG Long-Term Road Test

2005 Mercedes-Benz CL65 AMG Long-Term Road Test

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2005 Mercedes-Benz CL65 AMG: Another Quart of Oil Requested

June 13, 2014

2005 Mercedes-Benz CL65 AMG

Make that a liter. Our long-term 2005 Mercedes-Benz CL65 AMG popped up an alert on the instrument cluster to "add 1.0 liter of oil at filling station." But all I had was a quart...

Since said quart of 0W-40 Mobil 1 was previously placed in the car by some thoughtful editor (probably Herr Riswick), it made my job that much easier. Thanks, person!

So, why is the CL65 consuming oil?

Well, oil can only escape an engine two ways: it leaks out or is burned in the combustion chambers. Our CL65 is bone dry, so that means it must be being burned.

Some amount of oil consumption is a fact of life with internal combustion engines. It only signals a problem when the rate of consumption becomes excessive. Our CL65 had a quart added at 58,500, 59,000, 61,000, 62,000 and now 64,315 miles. Apparently our observed rate of oil consumption is (anecdotally) not uncommon among Benzes equipped with this twin-turbo V12 (known as M275 in Daimler-land).

Still, I can't help but wonder why these engines consume oil at this rate. Are the M275's oil control rings not as effective as they could be? Is the crankcase breathing system inherently inadequate (crankcase pressures push oil vapors into the intake at a high rate, rather than separating the oil mist from blowby gases and returning them to the sump)? Valve guides (there are certainly an awful lot of them in a V12...)?

I don't have the answer. If anyone out there is intimately familiar with these engines, drop me a line. I'm genuinely curious about what makes this engine tick. So to speak.

In any case, our CL65's engine is certainly strong. Check out the dyno test we ran on it:
Words:

Video:

Jason Kavanagh, Engineering Editor @ 64,315 miles

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