Audi-Impaired

While driving home yesterday (on the 1st day of using the AC) my oil pressure light came on. I was on the highway for about 1/2 hour doing 60~80 mph. I had to slow down for traffic, and shortly after that the car beeped and the oil light came on. While I was looking at the light, it went off. Well, I panicked and went to the closest gas station. Turned off the car and let if sit while I went in and bought some oil. When I came back and checked it, the level seemed fine. I found it very hard to discern a 'level' on the plastic piece, but it clearly had enough oil. ( I checked at least 5 times in a row)

I drove it home, checked it again. Checked it this morning and drove 40 miles into work this morning. No light, no problems. Also, the engine sounds fine, is behaving fine, and had an oil change 800 miles ago (I don't know what oil was put in..)

Could running the AC have anything to do with the light coming on? Should the light stay on if I have an oil pressure problem? What could have caused the light to come on.

Thanks for any help.

Erik
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'94 90S 132k

samtheblur

Maybe the A/C put a greater amount of stress on it during your long trip.

MikTip

Quite possibly something wrong with your oil pressure warning system? After all its electro-mechanical! A bad oil pump is very rare.

Probably the wires on your oil pressure sender, or the sender its self? Maybe a wire, or the unit inside the dash?

Audi-Impaired

Could the light go on if I have the wrong oil for the outside temnperature? It probably has 5W30 in it, and I noticed the manual says not to use it above 80. Today it was 95. The manual also says not to use that oil for long highway trips. What do you think?

-Erik

tpierce

You should be using 20w50/15w50 in summer, 10w40 in winter. 5w30/10w30 is too thin...

Corey T

I had a similar problem with my 93 90cs. The wires coming from the oil pressure sending unit were in contact with the compressor pulley. The pulley rubbed off the inslulation and was grounding out the circut. Figured this out myself after I paid a mechanic $200 to change the oil pressure sending units. Needless to say I gladly spent the money for a Bentley shortly thereafter.

MikTip

Your oils viscosity will thin the hotter it gets resulting in lower oil pressures. Quite possible the problem.

I run nothing less than 10w-30, Mobil 1.

ARK

Either oil viscosity is too low for the temperature, OR the pump or bearings are worn.