Sorry if this has already been discussed, I've seen a lot of posts about it but not many answers. I have an 01 A4 1.8t and suddenly one day my oil pressure light came on (and then went off again). I also noticed that my oil temp isn't registering (either that or my oil is really...really cold, all the time). What might cause both of these things together? Wrong oil viscosity? Bad sensor? Please don't say sludge. There are absolutely no ticks or otherwise out of the ordinary noises coming from the engine. Thank you for your help!

Here are the cliff's notes for people who don't like long paragraphs:

- oil pressure warning illuminated
- oil temperature bottomed out/not registering
- no weird noises
- recent oil change
- wtf

 

Not sure if this helps, but...

I didn't have the oil pressure warning light up, but my temp gauge was showing no movement. At the next oil change I replaced the oil temp sender (which doubles in my '00 A6 2.7T as an "oil level sensor") and the gauge started working.

This part is located on the bottom of the oil pan on my car and has three (or was it two?) bolts that hold it in. Once the oil was drained I just pulled the part and installed the new one before refilling the oil.

I don't know if the two issues are related on your car, but it would be an odd coincidence if they weren't. But I can't think of any one problem that would cause both a pressure problem and a temp problem at the same time, except maybe a lack of oil. Just to be safe, check the oil level at the dipstick and make sure you're not low. Maybe the oil pan plug wasn't properly reinstalled after the last oil change.

P.S. Thanks for the Cliff's notes.

 

I did a full oil change, put some 0w-30 (was running 5w-30) and new oil filter in and it seems to be okay now. It is ungodly cold here, would sub zero temp cause problems like this if I'm running 5w-30?

I should also add that the oil pressure lamp would only light up when the car was warm & had been running ~30mins. It would first be lit intermittently and then more or less consistently, and would go away for a little bit if I turned the car off and let it sit 5 or 10 minutes. But I guess the moral of the story is is that it all seemed to be related to the temperature of the car.

Does this make sense or should I take it in to get looked at?

 

It sounds like you may have fixed the problem with the thinner oil. If the warning light stays off, you've probably fixed it.

Remember, though, that since your problem is happening when the car has been running for a while, you didn't really change to a differentoil. The "30" in 0W-30 and 5W-30 means that when the car is warmed up the oil is behaving like a 30 weight oil.

Maybe what's happening is that the 5W wasn't thin enough in the cold temperature to flow properly and after a while you'd get a warning. Now with the 0W you're getting better flow when it's cold and fending off the warning.

Give it a few days and see what happens.