Oil Weight + Oil Pressure

'89 Audi 200TQ:
It is possible, or likely, for the oil pressure warning light to illuminate and the warning chime to sound because of a change in engine oil weight?
I was running 10-W40 Quaker State which I just put in during an oil and filter change. Intermittently the warnings started going off and the oil pressure was lower than it had been previously. When the warnings would go off, it was almost always associated with revving in 2nd gear to shift to 3rd.
I switched back to 10-W30 and all is fine. I could not get the car to do the same thing.
For my climate the manual suggests 15-W50 or 15-W40, but it seems my car doesn't like it. Or maybe I have a failing sensor or oil pump.
Thanks for your ideas on this,
Bill Graham --------------- 1989 Audi 200TQ
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The failing sensor or oil pump might be the case. It might be because the oil filter you installed has more restriction than the spec calls for. At the AudiWorld forum there have been several comments that claim the Mahle oil filter and another brand I don't remember are supplied by Audi and are higher capacity and flow than the typical ones that are available in the after market.
This might be more critical in your Turbo.
Tony '91 100Q 5spd Using an Oil filter from my local Audi dealer and Mobile 1
Bill Graham wrote:

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I did just switch back from a crud filter back to the Mahle filter (black with white type, OEM) when I put in 10W40. Same filter is now being used with the 10W30. I think I'll stop by and see the Audi folks today and pick their brains a little on this subject.
Thanks,
Bill

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The 'switch' sensors in these cars are notoriously cheap and fail regularly. If the oil pressure gauge (a different sensor) says it's OK, it probably is. The chime/light sensor is a *switch* and it's basically cheap junk. Try swapping it with a new one (no *better*, but at least it's new). For those who don't already know me as the Cheap BastardTM) I am, the reason is simple: the cost of replacing this thing (which is the *most likely* component to fail) is cheaper than even the diagnostic testing for everything else. -- C.R. Krieger Been there; done that.
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