Hi, I just upgraded from an 86 5000 to a 2000 A4 1.8t quattro. It has been running fine. I changed the oil and filter yesterday(M1 10w30) and it ran fine. Today I was driving and the CEL came on and I noticed that when I was driving the oil temp gauge would rise rapidly then when the engine was at idle the oil temp would drop rapidly, the other temp gauge is static at 1/4. This doesn't seem normal, it is 10'f here today but still it seems strange to me. From what I can see I didn't knock any of the sensors loose.

Any help would be appreciated

 

10/30 is too heavy try 5/30 or better ( full synthetic )