LT1 experts, have a question about oil pressure

FIL has a '95 Roadmaster Estate. I drove it up from the coast yesterday towing a utility trailer (it never broke a sweat). But once we hit some stop-and-go traffic south of Atlanta I noticed the oil light was flickering/on whenever I came to a stop. Tapping the gas (and therefore the RPMs) made the light go out.

The car has 191k on it and he runs 5w30 Mobil 1 in it. I'm thinking the motor is starting to show its age. He lives on the Georgia coast where it rarely goes below freezing, so I was thinking we swap it to 10-40 Mobil 1 and see how it behaves on the drive home.

I know it is a bandaid, but a rebuild isn't in the cards right now.

Personally, I'd put a mechanical oil pressure gauge on it and find out what the pressure really is before doing anything else.  

Word.

That and thicker oil in the mean time.  If it's just seasoned and not knocking there is still plenty of life left in it.

rslifkin said:

Personally, I'd put a mechanical oil pressure gauge on it and find out what the pressure really is before doing anything else.  

This.  It's silly to try and fix or even band aid the problem without knowing what the problem actually is.

10-4. I'll crawl under the whale and see where I can attach a mechanical gauge. I think I have one sitting in a junk drawer somewhere in the garage.

I believe there is a port on the block directly above where the oil filter screws on on the driver's rear corner of the block.

I hate to be that guy, but all these years have taught me you have to ask the questions or you don't get the answers.

Did you check the oil level?

I had a bad sending unit on my '89 C1500 Chevy Truck.  The oil pressure light would flicker on at idle, and would go away once underway.   Once the sensor was replaced, everything was 100%.  It never made any knocking sounds, etc.

The oil pressure sending unit on my 88 Silverado 350 is erratic. Does okay for a while after I replace it, then starts to bounce around. 

Good advice to check it with a mechanical guage. 

Yah gm oil pressure sensors can do that when failing, but really the first step is verify pressure with a mechanical gauge, well thats after verifying oil level.

My '95 Roadmaster challenge car with the LT1 started doing that same exact thing in traffic, with the same oil, only a few hundred miles after the engine rebuild. I had not replaced the oil pump during the rebuild on the 250k mile motor because Challenge budget. I ignored it and just kept the RPMs up in traffic.

It developed a rod knock within weeks. Verify your oil pressure first. Maybe change to a thicker oil. Maybe your oil pump is going out. 

The oil pressure sending unit is behind the intake manifold. A bit hard to reach, but you can unscrew it and plug in a mechanical gauge there.

If the pressure is verified as being low, a new high pressure oil pump should buy you some more time. 

Right, instead of fixing the leak just supply more fluid.

 In all of my years playing with engines I never found the oil pump to be the cause of low pressure.   Relief valve a couple times.

Wear has just caused more leaks than the pump can supply.

Won't the lifters start clattering if pressure really is low ,or don't modern units do that ?

I would say if you're pulling the pan to replace an oil pump, might as well spend the $50 on some new bearings too.  Its a band-aid fix putting new bearings on an old crank, but it works.

An old-school fix for an old school engine

My father's Olds wagon (OK, it was an '85, not a '95) would do that at idle when it was overdue for an oil change, regardless of oil level.  Fresh oil usually made that problem go away for another 5,000 miles.

Keith Tanner said:

I hate to be that guy, but all these years have taught me you have to ask the questions or you don't get the answers.

Did you check the oil level?

Hehe, yup, first thing I did. Oil level is good.

Car runs great. No odd engine noises. I haven't checked the oil pressure yet because it is stinkin' cold outside. If I use the pressure sending unit to check the pressure, I may just slap a new sender in it for good measure.

Ive never really heard one clatter unless oil was low, these things have a dumb low minimum oil pressure spec. Its like 6 or 9 psi at a hot idle.

At 109k if its been maintained i really doubt its worn out, i didnt cam mine til 108k and then i proceeded to rev it to 7k daily for the next 100k miles, no problems, and we found evidence that for part of its life it had a blower strapped to it.

I have abused the snot out of my 96 LT1 with 150k.  Either my oil pressure is fine or the light bulb blew.

What oil did you guys run in your LT1's?

I always used 5w30, and usually just one of the brand name mineral versions; castrol and valvoline are my usual go-to flavors.

At somewhere about the 30k mark I decided to let the computer tell me when to change the oil.  It took a long time and made me nervous.  I got to 6000 and changed the oil but didn't reset the light because I wanted to know when IT thought I should do it and it clicked on around 8000.  For one oil change I used Mobil1 and figured that would get me through to when the computer said to change it, but again, I got nervous at 6000 and changed it anyway.

Now the way I do it is change with Castrol regular stuff every 5k and ignore the light.  When it comes on I just reset it to get it off the dashboard.

For those who don't know, the change oil light in GMs isn't an oil tester, its a set of algorithms in the computer that measure a bunch of things like average miles per trip, average temps, throttle position, etc to determine when it THINKS you should change it based on your driving style.

My Fiesta's light is simple.   Tells you when you get 10K miles from the last time you turn it off.   I think it might be one year also.

No way to set it to when you change oil.

I ran pennzoil platinum 5w30 in mine, at 4 to 5k intervals.