Quote:
Originally Posted by anom3
i have mentioned this previously in some replies, but thought i would throw it in:
there is no doubt in my case this is somehow related to the oil system.
after switching over to 0w40 the noise is much different.
a) quicker and quieter, every time. in the last 15+ cold starts, i have yet to have it 'really bad'. i know 'really bad' is subjective, but there has been a clear and definite improvement over what it was like before.
b) the noise 'doesn't happen' quite a bit more frequently now.
c) the car can sit for a bit longer and not exhibit this noise.
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Yep, this definitely corroborates it. Not sure how familiar you are with oil ratings, but there's a gross simplification:
0W-40
The "0W" part is how the oil flows when it's cold. An oil rated at "0w" flows like a straight 0 weight oil at operating temperature.
The "40" part means the oil flows like 40 weight at operating temperature.
The lighter weight oil flows more freely past orifices in the engine that maintain oil pressure in the various systems. This is a dual-edged sword. Oil that flows more freely will result in a lower oil pressure when run through the same engine. However, this isn't always a bad thing when talking about the low-temp rating of an oil, because the oil already flow so much thicker when cold.
It sounds as if the effect in your engine is that the free flowing oil is able to flow in to whatever systems are causing the knock more quickly, which prevents the clacking altogether.