Oil Pressure Question

[88-GT]

Hey just trying to figure out the best thing to be doing for my motor on oil use. AS it sits now I have some Castrol GTX 10w-30 and my oil pressure is decent but not as good as I would like.

As far as I know the bottom end has never been touched and the car has about 195000 Kms(115000miles) and with the above oil I usually get about 18 psi at hot idle. Its wierd though, when cold its always a solid 60 and as soon as I even rev it up to 14-1500 rpm when hot it jumps to 60 almost instantly. Just at idle once warm it gets a little low.

I have heard this could be due to warn out bearings in the bottom end but could it be a weak oil pump? I am also thinking of changing oil to some 20-50 too, any opinions on that?

 

[HISSIN50]

Your thoughts are mine too.

As far as 20W-50, if you live in a mild climate, go for it. I run 20-50 in the stangs almost year around (desert SW. Summer highs are ~115*F and lows seldom below 70). You could also try running 10-40 first to see how it helps pressure. I would take small jumps in viscosity, esp since it is cooling off in most places (unless you are in Australia, where it is Spring heading for summer. ).

Good luck.

 

[88-GT]

Think there could be any truth to the weak oil pump theory or just the miles catching up to it?

 

[ninety15.0]

well what do u think is actually changing when you say "the miles are catching up" all the tolerances in the motor are not what they used to be and that includes the pump. The pump theory and the miles catchin up theory are one and the same...

 

[Roland69]

I tried doing the 10W-30 to 20W-50 thing mine dropped in pressure a bit by doing so. With the 10W my oil pressure was at the M in normal at hot idle I don't know what that would be in psi.After switching to 20W-50 it sits just under the M. I think because it's thicker the pump wont pump it as fast or as hard. I'm going to try 10W-40 or maby 15-40 Mobil1 red cap or Castrol syntech

 

[Roland69]

Oh yea mine is an 88 GT with 180K

 

[sgarlic]

I tried doing the 10W-30 to 20W-50 thing mine dropped in pressure a bit by doing so. With the 10W my oil pressure was at the M in normal at hot idle I don't know what that would be in psi.After switching to 20W-50 it sits just under the M. I think because it's thicker the pump wont pump it as fast or as hard. I'm going to try 10W-40 or maby 15-40 Mobil1 red cap or Castrol syntech

Well, 10w30 would mean at operating temperature the oil viscosity will be 30. With 20w50, it'll be 50 (thicker.) The reason people need higher viscosity oils is usually because they can't maintain adequate pressure at hot idle (like my wife's Jeep.) The oil thins out too much, and flows faster (little pressure.) Theoretically, with something like 20w50, the oil would be thicker at hot temperatures, and flow slower (more pressure.)

With that being said, I wouldn't rely on what your stock gauge tells you anyways.. if you have oil pressure concerns, you might as well just pop an autometer gauge in there to make sure.

 

[HISSIN50]

Roland, with all due respect, interpolating the stock guage is as useful as tossing darts while blindfolded. The IVR and poor calibration make the gauge about useless.

The 20-50 should be giving you more pressure across the board, except at initial start up, if it is cold where you are.

Good luck.

 

[Roland69]

That makes sence Sgarlic thanks for filling me in on that
I know my stock gauge is as useless as having a Chevy with a 305 or tits on a bull. I wanted to put in some new gauges when the funds are better.