(Oil level is correct)
I recently bought an A4 B6 1.8T Q with 36k miles. I have put on about 2500 more.
The oil light 1st came on after driving for about 5 hours with only 1 or 2 short stops. I was going about 80-85 mph when it came on. I pulled over and the level was about in the middle of the hashes. I topped it off with oil that was in the trunk from the previous owner (it wasn't synthetic) and started driving and it came on within a few minutes. I stopped again and waited a few minutes and then drove another 1.5 hrs at a slower speed with no problems.
I then changed the oil myself replacing the Audi filter with another one from the dealer and filled it with mobile1 5W30 (even though the service notice on the dash says it's not due for more than 200 days and over 6000 miles). No problems on the return trip and a couple of shorter trips, but then this weekend it came on again after driving about 5.5 hrs. This time I was in the mountains at 50 - 60 mph and it would come on for a few seconds at a time, only when the engine was straining to get up hills.
The engine doesn't seem to be burning any oil.
When I was buying the car I think the previous owner said he had had the oil pump replaced (I have a terrible memory). I don't know why that didn't raise any alarms in me, but he is a friend so I wasn't in skeptic mode.
I wish I had removed the oil cap and peeked inside the engine before buying it, because it is very sludgy in there. I scraped some of the gunk away with my fingernail and it still shows 1000 miles later. I'm thinking that is the problem and the oil pump was probably fine.
What kind of sensors turn on the oil light? Level and pressure?
Thanks
--Art