I got down to reading that the oil pump screen may also be clogged.
How could this happen if I always run synthetic 5w-30 and change the oil and filter every 3-5K miles?

 

the sensor doesnt really get clogged like something mechanical would. just the electrical sensor circuits inside that convert pressure differences to electrical signals burn out over time and heat cycles. if its faulty there isnt much you can do to fix it. if you actually have low oil pressure not just a bad pressure switch, its not good to drive around with.

i wouldnt drive around very much with seafoam in the crankcase. seafoam is pretty much just pale oil and naptha, neither of which would protect any better then some quality synthetic oil. seafoam will however break down solid gunk faster then synth oil. i would put the seafoam in there and let the car idle for 20 minutes, maybe go for a short drive. if it hasnt worked by then its not going to.

i dont know about the diesel thing. i wouldnt put fuel into my oil, ive never seen anyone do it to an audi, not sure what would happen or the long term effects of having that much flammable hydrocarbons and VOCs in there. im sure there would be diesel residue in your oil for many oil changes afterward. also not sure what diesel would do when it gets pumped thru the bearings in a blazing hot turbo.

 

Anyone else have any ideas?
I'm going to check the actual oil pressure readings tomorrow with a gauge.
Then I'll decide if the pressure sensor is bad or not.
If the readings are low it's going to be thick oil and car for sale.

 

i think you should take off the pan and take a look. think about it this way, if it's not the sensor and you replace it now and drive it, the cams will get dried up and eventually freeze on you. you'll eventually need to take off the pan so do it now and hopefully save you engine or you could risk killing your engine. a cup of seafoam and driven only 3-5 miles isn't going to do anything useful. the seafoam needs to go around the engine for about 50 miles so you're way off. the sensors rarely go bad though and the 1.8t engine is a sludge magnet even if you're using full synthetic.

 

My 2.8 started that nonsense around 180k miles or so as well. It was getting low pressure lights in the summer heat. I switched to 10w-40 and it improved somewhat but it still would come on occasionally when it was 100+ out. I then went with 20w-50 and I think it has only come on once in the last 30k miles.

 

I disconnected the oil switch this morning. It had a little oil in it. I sprayed the switch and connector off with electronic cleaner spray.
I drove the car to pick up a new switch - 50 miles round trip and the oil light didn't come back on until I was almost home.
I removed the switch (electrical connection full of oil again) and installed a cheapo sunpro oil pressure gauge.
I was reading about 20 psi at idle (engine warm), and up to 70 psi at 3000 rpm, maybe around 75 psi max at 4,500 rpm while driving it.
I think this is ok pressure, maybe to the low side of the allowable pressure, but I think ok for 182K miles.
I put in the new oil pressure switch after cleaning off the connector again.
It's been nearly 3,000 miles, so I'm going to run some Solder Seal Gunk Motor Flush for 5-10 minutes (as soon my engine cools down) then change the oil and filter.
I think I'm also going to use a synthetic 10w-30 from now on, at least for the hot summer months.

 

reply two weeks late... but...

I thought that the first number was the cold viscosity and the second was the warm viscosity. So the 10w-30 would act like a 10 weight oil when cold and a 30 weight oil when hot so as to have a somewhat even viscosity as the engine heats up. If you want to have a bit thicker oil and higher oil pressures at high temperature, then you'd want a 10w-40, or a 20w-50 right?