Well i have just been recently driving my 94 Z28 A4. It has 113,000 on the clock. When i 1st start the car oil pressure is around 1/2 the after warming up it drops down very close to but above the 1/4 mark when moving and when i stop moving the guage shows its just below the 1/4 mark. Im running that new 10w-30synthetic blend mobil oil that is supposed to be good for 7500 miles. This is my 4th LT1 Z28 and i never noticed anything like this before. Any help or info would be appreciated thanks!

 

mine was like that at one point, motor didnt last to much longer.. killed all my bearings..

 

wow, I have a '94 Z28 (LT1, Auto) also I have this same exact problem. I've yet to figure out what is causing it. I've even had a few days that it's caused my check guages light to come on then go right off. would be nice to know what causes this.

 

What would you guys qualify as a "healthy" oil pressure for a LT1? I've seen a few LT1s running around where you described in the oil pressure area and they've seemed to be very healthy engines. I wish i could walk outside and check my guage just to make sure I'm visualizing it right, but I totaled my Z a while ago.

So anyone who knows a little more than I do- what is a good oil pressure for an LT1? Where should the needle on the guage be?

 

the first thing i would do is put a mechanical oil pressure gauge in the oil pressure sensor port to see what the actual pressure is, you may just have a bad sending unit or gauge.

 

mine does that too. On hot days, when the oil is thin, the pressure drops so low the check guages light comes on. and i run mobil 1 10w30. Its done this for a couple years though, and so far no problems. I have replaced my sending unit and it did absoultely nothing for the problem, so it wasnt that. I guess it could be the guage... I dont know.

 

right after i had my engine rebuilt it was right around where your oil press. is. unless u hear pinging or knocking i wouldnt worry too much. if u have 10lbs. of oil press. to every 1000rpm's the engine shouldnt be oil starved, this came direct from my engine builder. also id try the mech. oil guage if your worried.

 

Try some 20-50 oil of another brand,and don't drive it until you know for sure what the pressure is. Should be at least 20 at idle and 40-45 going down the Interstate at 70mph.

 

I believe synthetic oil is actually a little thinner than the reg stuff.

 

it is, but it keeps its viscosity at higher temps better, and it alot less prone to viscosity break down. So when its cold its thinner than mineral based, but when they both get hot they are about the same give or tak

 

Well you could just leave it alone and see if it lasts. Won't last long with low pressure.

 

On a fresh cold start in the morning, my '95 Z28 w/ 111,000+ miles shows just slightly under the 3/4 mark on the gauge (which is normal because the oil is so thick after sitting over night).

Once fully warmed up, it reads right at the 1/4 mark (20ish psi) at an idle, which is what it should be...If the car has been running for a very long time, it might drop a little below that, but nothing to worry about...

Again, when fully-warmed up, part-throttle around town reads 1/2 (40psi) at about 2,000rpms and a good 45psi a little above that...Full throttle is definitely over 50psi if I remember correctly.

Anyways, if you're getting a solid 18-22psi at a hot idle, 40+ under acceleration, and at over 50 at WOT, your LT1 is perfectly fine IMHO.

BTW, I don't know if there has been any change with this new, long lasting version of M1 10w30, but any of the M1 10w30's of the past are really more of a 20 weight oil in reality as they thin out VERY fast (which will not help your cars oil pressure at all). With the M1 5w30, my LT1 would show a noticeably lower oil pressure reading at a hot idle than it currently does with the 0w30 German Castrol Syntec I run now. Something like the GC 0w30 (really more of a true 40w in actuality) or M1 0w40 are proven, very good oils that will help your high-mileaged motor out considerably with oil pressure and engine wear at high operating temps FYI...

Mike

 

thanks for the info. Im gonna go check out a few things soon. I did also mix 1 quart of 5w-30 with 4 quarts of 10w-30 think that has something to do with it??

 

thats how mine runs. After fully warm at about 900 rpms it sits just a hair under the 1/4 mark.

 

From GM service manual:
These are minimum oil pressures
6 psi @ 1k RPM
18 psi @2K RPM
24 psi @4K RPM

Low isn't it!