It's the slight gurgling/grinding noise that's getting to me Winfred. After I had that cold-start problem where the oil pressure light refused to go off for 10 seconds idling and I could see no oil squirting up top through the filler hole, I noticed a nasty scrounging noise down below which I described at the time as cavitation noise. After swapping to 15W/40 as you suggested it's much better (no noticable noise since) and the idiot light goes out in just on 1 second at 25 degrees C / Warm day. However the light oil makes the (new) valvetrain noisier at temperature on a hot day so I am not happy to stay with 40 weight during the summer. I am worried that if I go back to 20W/50 I the pump may not oil the engine well- and am a tad worried that it is blocked or losing pressure somehow. Using a stethascope on the motor it sounds like there's a bit of a party going on inside the block, but you have to use a stethascope- trying hard you can just hear it with an ear near the sump underneath. I guess I should swap to 20W/50 and see... and perhaps go and listen to another M30... what do you think?Originally Posted by winfred
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