Was this problem ever resolved? I am having a similar problem with my oil pressure light coming on after 20 minutes of highway driving. It only comes on when I accelerate, and turns off when I let off the throttle.

 

I have already pulled off the oil pan and checked the pickup.

 

It could also be a faulty oil pressure sensor.

 

Don't mean to hijack your thread, but it seemed dead. Ok, I checked it tonight with a mechanical gauge. And sadly enough, the oil pressure light is accurate, meaning the wiring and switch are all ok. I had next to nothing for 10 seconds on cold start-up, and that climbed to 20 psi max. When it is revved up, the pressure actually drops!! I didn't let it run too long because the gauge fitting was leaking a little and I don't want to make too big of a mess in the driveway. I am sure that I would have seen lower numbers when warm/hot. So, I have a filter (I forgot it at work). It is a "Mann" filter (Actually an Audi filter, which is made by Mann) that fits older Audis. It has a steel spring inside for the drain back valve. So this is a much higher quality filter. Are we still thinking filter, possible clogged oil passages, worn pump gears, worn bearings? I don't think it is bearings, because the engine sounds and runs fine (for now). I think it may be worn pump gears or clogged passages. The pump cannot deliver the volume for some reason when the RPMs are raised.

 

I am also planning on using 15-50 oil

 

What weight oil are you currently using?
Where are you located?

 

Sorry guys for not getting back sooner, but I only scan the D1 site for my 98. “Was the problem ever resolved?” Well that is question which is always a work in progress answer. As posted I had low oil pressure by the mechanics gauge, the oil light and a very slight bearing knock. My mechanic did an oil flush (PO’s mechanic did 2 flushes, oil sensor and oil pump) and then we replaced the bearings, cleaned pan, oil cooler, checked everything at the bottom end. Then rechecking the oil pressure the mechanics gauge said cold 24 psi and warm 10 psi at 2000 rpm. I said WTF POS take it home and deal with this. I installed a Glow-Shift sandwich adaptor under the oil filter to allow the installation of 2 mechanical oil pressure gauges (different manufactures a 0-30 and a 0-60 psi). If the 2 gauges agree then that must be the pressure.
My gauges read (idle/2000) rpm 30/30 cold and 12/24 which is ok for driving but not there yet. My recommendations are not to trust one gauge or the mechanics gauge when close to the minimum pressures around 10psi. For my engine there maybe a problem of blockage around the oil sensor port and the hired mechanics may have done there best but did not get proper readings of the pressure. My cost was $30 for the Glow-Shift oil filter sandwich adapter http://www.glowshiftdirect.com/Oil-Filter-Sandwich-Adapters.aspx and two $10 mechanical screw in mechanical oil gauges. My next job is to reinspect the oil pump as the PO mechanic installed a new pump but reused the old cover. After that I will look at the top end of the motor. “What oil?” Rotella 15-40.