idle oil pressure jumps

[Cam1959]

Changed oil and filter few mths ago to 5w30 full synthetic as it clearly has easier cold starts.

At cold start, as always over many yrs, oil pressure goes to 80 psi... after warming up idle pressure has alwasy been 40 ... sometimes over last few weeks, when idling at red light, it jumps to 80 or beyond ... if i push brake and gas a bit to raise rpm slightly, oil pressure returns to normal 40 ...

It's a 1983 s10 blazer 2.8 v6 ... about 200,000 kms ... runs great ... i fear the above is sign that oil channels in block are partially blocked, needing more then idle oil pressure to maitain oil flow.

What you pros think ?

I was told to try Rislone for few days and oil and filter change after that.

[MT-2500]

Do not dope it unless you want to kill it?
Are you using a good AC-Delco oil filter.

Test oil pressure with a manual oil pressure tet gaauge.
Post back readings with a test gauge.

[bearcat329]

start with the simple things 1st, test with a manual pressure tester, then if that checks out ok, try replacing the oil pressure sending unit,and work from there, a fluctuating oil pressure reading is no real cause for alarm tho, my dads 92 chevy 2500/ with a 350 eng, has been doing this for years
hth
Rick, Ore

[Blue Bowtie]

Since you're on the other side of the lake in Thunder Bay, you might get away with a Delco filter. US marketed Delco filters have changed again, and it appears that Baldwin and Wix are the units of choice for now.

The pressure may be bouncing off the relief valve setting, but as previously advised, test the actual pressure with a mechanical gauge to verify.

Stay with the synthetic (as long as it is actually PAO-based synthetic) and avoid additives. The engine will eventually get cleaner.

[blazes9395]

Blue I didn't know that about the AC filters....I just made a trip acroos the border and stocked up on some 47's and 52's from walmart, they were the duragaurds on sale.

Cam, has the pressure sensor ever been replaced? I would venture a guess and say most likely its the sensor is on its way out. Verify with a mechanical guage like others have mentioned. A good PAO oil up here is the Esso 0W30 XD3. Walmart carries it. The Castrol 0W30 is a great oil too. With the temps up there, these oils flow great too.

Let us know how its goes!

[Sparky1349]

Hey Cam,

I had an '83 S-10 2.8L and a '87 s-10 2.8L and both of them failed the oil pressure sender. When the sender completely failed they went to max pressure and stayed there. When they were on their way out they jumped from normal to high pressure a lot especially at idle. The oil pressure sender is easy to get at, it is right next to the oil filter so you can reach it throught the wheel well by lifting the rubber splash shield (easier with the tire off). With the age and the mileage I am not surprised your having problems with it since everyone I know had to replace the sender at well under 100,00 miles.

If this is the fix but you decide to treat the oil anyway I have had good luck with SeaFoam. If you have never used it be sure to change your oil in 100-200 miles after you put it in. I used it on a 2002 Blazer to fix a noisy lifter but waited about 500 miles to change the oil and there was so much crap in the bottom of the pan when I pulled the drain plug nothing came out (but that lifter has been quiet ever since).

good luck,
Sparky