1987 S-10 Blazer 2.8 low oil pressure

[GM4Life]

Hey all, new to this site. I'm having trouble with my S-10 Blazer...

When I start the truck the oil pressure is fine...Indicator reads 40+psi, but after it heats up and especially after driving 10 or more miles on the highway, the oil pressure drops to it looks like 5-10psi. I've even had the check gauges light come on a few times.

It doesn't seem to affect how the engine runs...but I would like to get it fixed none the less. Any suggestions? Thanks.

[3100 MPFI]

sounds like the engine is wearing out. When the engine is cool, the oil is thick, but as it warms up, it thins out. You can probably put thicker oil in it (the 1988 2.8 in my Cutlass Supreme did that, and I got better pressure by switching to 20W50 oil).

I think there are quite a few things you can do to it, but I think it is a sign the oil pump is getting worn out. I think the bearings wearing out can do that too, but first thing I would check would be the oil pump.

You could also test the oil pressure to make sure it is not just your gauge or sender is going out.

[geoffinbc]

Ehh I wouldn't worry about it. If you can maintain 10 PSI your fine.

There are some things you need to do to to keep you in the safe zone. First buy a GOOD oil filter. AC Delco, Wix or Donaldson. No Frams or Generic junk. You need good oil flow through the filter to keep good pressure. Second after you install the good filter and change the oil install a mechanical guage for a test. You can install it temporarily or permanently. But always keep it under the hood if it is going to be permanent. If you just want it for the test you should be able to borrow one at a parts store with a tool loan program. Do the test at full temperature at idle and see what you get. Even 7 PSI will keep you in the safe zone as long as it is steady.

If your pressure is good but your gauge reads low then replace the sender. If your pressure is a bit low I would keep the oil you are currently running and add some Lucas oil stabilizer. It will increase the film strength and help thicken up the oil. 40 or 50 Weight is a bit much and should only be used if your pressure is really low or bouncing off zero.

[neo71665]

Same year and same problem. Just run thicker oil like said.

[GM4Life]

That's for the input guys...I've been reading a lot of forums online and they seem to point to the oil pressure sending unit...is that difficult to repair? Should I take it to the dealership or a mechanic?

Also when I change my oil what do u recommend if not the 40 or 50 weight?
Thanks.

[3100 MPFI]

I don't know about your S10, but in my Cutlass Supreme, the oil pressure sender was right next to the oil filter. Took nothing to change if you did it with an oil change.

For oil, back then I used just whatever was the cheapest. I didn't really care about saving the engine so much seeing I was building up my 3100 at the time. I just used whatever was on sale in the heaviest weight I could get (which was 20W50). I usually used the pepboys brand, or Pennzoil.

I also tell people to keep away from FRAM filters. I get ACDelco filters for my cars (good ol PF47 for the 3100, and good ol PF52 for the STE). In my area, O'Rilley's Auto Parts carries the ACDelco filters.

[neo71665]

I run 20w50 in mine. The oil pressure sending unit prolly aint bad. Most of the time when they go out the gauge quits working or they start leaking oil. Depending on if you got the 2 or 3 wire one you might not wanna replace it. If I recall correctly mine was a 3 wire and $60, we had to go to 4 or 5 diff places before I finally found somebody with one in stock.