1992 bonneville oil pressure

i have a 92 pontiac bonneville that has developed a low oil pressure problem. when the engine is cold the pressure is at a normal 50 to 60 psi but when hot the pressure drops to 5 causing low pressure sensor to go off. what is wrong?

How many miles on the car?? What weight oil are you using?

it has 260000 miles and i use 20-50 presently. the car runs great except for oil pressure. i am concerned oil is not circulating to the valve cover area now.

Using a 20W-50 oil is probably taking out the rod/crank bearings and all other components in the engine that require oil at cold start-up.

A 20W-50 oil will build oil pressure in a hurry at a cold start-up, but it won’t flow fast enough to get to vital engine components to protect them. And 80% of engine wear occurs at cold start-up even with the proper weight oil specified by the manufacturer.


Is the pressure low just at idle or all the time? Does your engine make any disturbing noise on a cold start-up?

Basically, engines need 10 PSI oil pressure for every 1000 RPM.

Depending on your climate, 10/40 oil might be a better choice in the winter and save the 20/50 for summer driving.

It might be time to start shopping for a replacement vehicle…

Oil pressure on a cold start is 50-60 psi, after warming up it is approximately 30 psi while driving and drops to 5 psi (or less) when at idle. No sounds at start up but after driving there is a slight aroma of something hot.

Regarding replacement, I have another, but I bought this car new and can’t bear the thought of its demise!

I have the same problem on the Bonneville 1997. Although it is a serie II engine i believe it is a upper manifold issue. I wont be surprised if ur manifold is leaking some coolant into the engine!
When i first start engine oil pressure is up to 3/4 to max. After about a 30mn drive it goes down to almost red zone and engine starts to stall. And if i keep driving the check guage will light on. Normally i shut off engine for 20mn and im good to go again!
I use 10/40 engine oil…
I love this car and cannot change it now to get a newer car. Also im a sucker for these kinds of big sedans/ 3800 engines!
I also trust this could be easy to fix but no one seems to figure it out

Toni , this is a 9 year old thread and if you can’t get a different vehicle then why the thread about the Cadillac SUV.

I was posting the oil pressure issue then i saw this similar post so i went to reply on it!
As for the caddilac post i still havent made my mind about it after i saw many negative posts concerning the SRX on carcomplains.com
You are right that i should maybe create a new post for this oil pressure issue that puzzled me for years
The cadillac i posted about is considered really cheap in my country. The owner dropped price from 7000$ to 6000$
So really was tempting. So i posted for advice.
On the other hand a SRX similar in my country would worth 7500$ for a 2004 model

If the oil doesn’t look like a chocolate milkshake, there is no coolant getting in the oil. The bearings are worn, the oil pump is worn and the engine will destroy itself in short order. The only way to repair this is an engine rebuild.