I have a '96 DeVille with 117,000 miles on it and after not driving the car regularly for about 2 weeks with no known problems and a recent oil change, my oil pressure indicator light flickers on and off when the RPMs get down to about 625-650. Once the RPMs increase to about 800 the indicator light goes off and stays off. BTW, this happened yesterday and I was also running the air conditioner.

For the oil change, I change the oil and filter myself and have been doing this for a long time. I use Castrol Syntech and Fram oil filter. The oil level is where it should be.

Is this an indication of a weak oil pump? What else could this be?

Thanks

 

Wrong oil viscosity.

 

Wrong oil viscosity? I used 10W30 just like what is written on the cap and in the manual. Should I use a different viscosity than what the owner's manual and cap says due to high mileage?

 

The only two things I can think of are the oil pressure sending unit (or wiring to the unit) or a plugged oil suction screen. Since this car has probably had synthetic all its life, I would start with the oil pressure sending unit.

 

Here's an update...this only occurs when I am running the air conditioner. With the air conditioner off, the rpms are still around 650. Kind of weird.

 

verify pressure with a manual gauge screwed in where the oil sender is. Based on reading probably replace sender.

 

Based on my own years of vehicle ownership, I would suggest you 'pitch' the Fram filter.
I have a 97 Eldo ETC and 3 Ford F250 4X4 pickups. I always use AC Delco parts on my
Eldo and Motorcraft on my Fords. I got a deal once on some Fram filters and bought them,
and after an oil change on all 4 vehicles each one of them had a 15 to 25 p.s.i drop in oil
pressure with the Fram filters installed. I pitched the Frams and went back to OEM and
the oil pressure was normal again.

 

I agree. Replace filter with DELCO prior to oil sender replacement. Report back.

 

Yesterday I replaced the Fram oil filter with a Mobile 1 oil filter and test drove the car with the air conditioning on, and the oil pressure light did not flicker. The one difference that I had forgot about was that the Fram oil filter I got this last oil change was their extended life filter instead of the regular orange one.

Anyway, thanks for the help. I wouldn't have thought about changing the oil filter.

 

That is very interesting, thanks for sharing. I would not have even thought that the oil filter (being new and most likely a bypass type) would cause such a problem.