Expert: Roland Finston - 11/20/2011

Question
Hi Roland,
I have been reading a lot about the oil lamp issue on these cars and I have not really found any sort of solution. The first time the oil light came on in my car was when I was waiting at a light and the temp. gauge was in the middle. I stopped and checked the oil level. It turned out to be just below MIN. So, I added a quart of oil to bring it back to the max level. I still got the light as soon as the oil was hot and I was at idle. The next day I took the car to Strauss and they told me the oil pressure sensor was leaking and that would fix it. So they changed the switch and changed the oil (10W-30) and oil filter. The light seemed to have went away but I could not tell because I didn't get the engine hot enough.The next day as soon as the engine was hot I again got the light at idle. The car idles at just above 500rpm.
I have seen some fixes involving a special part, changing the type of oil, fixing the idle rate, and everything in between. I am totally confused as to what the real problem is and if I am doing any damage to the engine by driving with this condition. I asked Kevin yesterday because you were maxed out but he only led me to some forum which only further confused my issue.
Thank you,
Frank

Answer
Hi Frank,
Your experience is common so it is correct to question. The minimum pressure is supposed to be 5 psi at curb idle rpm. I have yet find the spec for curb idle, but if it is smooth let us assume that yours is correct. In any case you can't control it as it is set by the computer.
Exactly what the psi is for the sensor to click the light 'on' is only known by testing it, but I suspect it is higher than 5 psi. The only way to know for sure is to screw in a calibrated gauge in place of the sensor to see whether that shows 5 psi or more at idle.
But in my experience if the light goes off when you lift the rpm to 800 or so as shown on the rpm gauge then I would not be concerned. If you want to eliminate the warning light problem you could use the next higher weight of oil (20W-40) at the next change as the pressure at idle will then be higher for sure.
Roland