Started last week after I had the oil change and fuel system update on my 98 ML. Occasionally, there is a high pitch squeaking noise (sounds like brake squeaking)coming from the belt/pulley area. I know it's not the a/c compressor since the noise persist even when I turn the a/c off. Nor it's coming from the brakes, the noise exists when the truck is stationary. Is there any part (pulley, crankshaft pulley, etc) needs some lubrication? The truck drives fine though. Any thoughts.