I have a 2000 c230k 73k miles - oil light is going on around 3500 rpm (80-90 mph). If I back off, the light goes off around 70 mph. Similarly, if I put her in neutral, the light goes off. Oil level is o.k. - not too high or low.

Could this be a bad sensor? Does the sensor measure oil pressure (which would suggest I'm losing pressure)? Could the oil filler cap be losing pressure at high rpms?

Help. Thanks

Well physics would say that at that high of an rpm you are sucking more oil out of the pan than is draining back into it. Could be too thick of an oil viscosity or clogged oil return ports. The only way to know if it's really losing oil pressure is attaching a mechanical oil pressure guage...that would rule out a faulty sensor.

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1999 CLK 430
W208
113. Engine
105,000 Miles
Raptor 245/40/17

Just an update. AFter much research (and direction from Gilly - thanks) it turns out the the light on the 2000 c230K only indicates level and not pressure. THis came from the dealer. Further, the oil pump is mechanically gear driven so chances are it will either work or not work (vs being intermittent which is what the light is doing). Further, you would probably see increased temp which is not the case. I'm ruling in favor of faulty (shorted) sensor. Not probs to date. When I find out more, I will post.

What about when you get it up to 4500 rpm and then back off to 3500 rpm... light on or off? (Do it in a lower gear if you don't want to get a ticket btw )

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-Marty

1986 300E 220,000 miles+ transmission impossible
(Now waiting under a bridge in order to become one)

Reading your M103 duty cycle:
http://www.peachparts.com/shopforum/showpost.php?p=831799&postcount=13
http://www.peachparts.com/shopforum/showpost.php?p=831807&postcount=14

this happens when the oil level is just beginning to get low, you mentioned that the level is ok not too high and not too low so I take it it's somewhere in the middle? if that is the case then this is normal for the light to come on. As mentioned earlier at higher rpm the oil pump is distributing the oil at higher rate so the level in the pan goes down. It's not a problem with return ports or anything it's just that you have more oil circulating around the pistons and etc as opposed to sitting in the pan. top off the oil to the max line and your problem should go away.
What this brings to mind is, is your engine using oil? if so you need to keep an eye on the level and keep it at the top line. but that light coming on at high rpm is kind of a good indication of oil getting low.

that sounds right on to me.

i would also check my return ports from the head to the pan for restrictions.

i know a guy who ran a chebby motor out of oil to the bearings by running a high rpm on a race track. all the oil got stranded in the valve covers and pow! the bottom end starved and broke big time.

good luck

tom w

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.