Oil pressure drops as it warms up?

[Big Roller]

I bought a 99 tahoe from a local mechanic with 260,000 miles on it for 1,500 bucks... Had a blown head gasket. He fixed it and I've had no other problems with it... Until recently. On cold starts, the oil pressure goes up to 60-65 psi. But as it gets warm and gets up to operating temp, the oil pressure slowly starts going down... After 20-30 minutes of driving, it will sit around 20 psi at 1500 rpms, but will drop below 10 psi at idle? The pressure also goes up as rpms increase. I've read so many different threads on here that I don't know where to start looking. Has anyone else had this problem before? Any help is much appreciated!!

 

[AZ Tahoe]

Its not a problem at all. This is normal.

 

[ezdaar]

Negative. anything below 20psi is bad! You should be around 40 at idle.
I would not be driving that tahoe on such low oil pressure.
Pour a can of seafoam in the oil fil and baby it for 2-3 days of driving, be warned of potential oil leaks.

Then change oil filter and oil asap! Heck the filters are cheap enough, change it before and after the seafoam treatment.

ACdelco PF48 (GM break in filter) or PF63 (GM replacement after break in).
These are OEM replacements and have the larger oil passage holes but are identical other than length.
Switching to this Always brings the oil pressure up, sometimes substantially vs other brands.

Example. Just did a oil and filter change on a friends truck. he had 19-21 psi at idle.
Changed to mobile 1 10-30 from what ever he had in it and from some pos fram filter to the PF48 he now has 41PSI at idle.


If doing the above doesn't help. you have a oil pump failure coming.

 

[Big Roller]

Oh boy... I'll definitely try the delco filter. I changed the oil about a month ago, and that's when the problem started. I just used a purolator filter(used to work at Sears auto, and that's all they carried), and assumed that would be okay. I get paid Friday so it has to wait until then.

 

[ezdaar]

shit, forgot that 99 was change over year.. what engine do you have 5.7 or 5.3?

The Acdelco PF48/63 will not fit the 5.7.
Either engine,, 10psi is really low.

5.7 Acdelco filter, 5$
http://www.autozone.com/autozone/pa...N-jd17lZ8gcsg?itemIdentifier=287813_177784_0_

 

[Big Roller]

5.7. I used 10w30 when I changed it last, and I don't know what the previous owner ran in it. Should I bump up to 10w40?

 

[ezdaar]

nah

 

[TraumaTruck1]

Purolators can are known to be restrictive. That could be your problem. You might could try to get just a filter and a quart or two of oil to top it off.

Did you check to make sure that the oil level isn't low?

 

[mattluttrell]

This might be wrong advice, but I've bumped up the weight in old small blocks to get my oil pressure back. I'd go back to 40W and see what happens. I certainly don't see it being a problem in summer. I might go higher if 40W doesn't work. I try to keep all the needles facing up if possible.

 

[Big Roller]

Oil level is full, so I know that's not the problem. From what everyone's said, I can also rule out the sending unit, correct?