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Oil Pressure Question

Joined
May 6, 2002
Messages
129
Location
Simi Valley, CA USA
Corvette
1975 Red on RED Coupe
My oil pressure gauge reads just under 40psi at start up and after is warm it ranges between 15 and 40 depending on the condition (stop ,Park Full throttle) Does this seem low to anyone eles or should I delve into it a bit deeper. You know :

"If it ain't broke, fix it til it is"
 
S

sac001

Guest
On my 80, at start up my gauge will read 80+, after warm up will fluctuate between 40 and 80 depending on engine RPM. My guess is either someone has been in there, or a faulty gauge. The oil looks good, and when I had the valve covers off there wasn't a bit of sludge, so I figure all is well regardless of what the gauge says.

Steve :w
 

Nut

Well-known member
Joined
Oct 15, 2000
Messages
890
Location
Bowie, MD
Corvette
Vette-less for now
Wicky.... it's perfectly normal.

........ Nut
 
Joined
May 6, 2002
Messages
129
Location
Simi Valley, CA USA
Corvette
1975 Red on RED Coupe
Thanks guys.. It Sure is great, that those of us who are trying to learn these cars have a place that we can go to to find out the information. Thaks Again. Jim
 
J

jmp

Guest
sac001 said:
On my 80, at start up my gauge will read 80+, after warm up will fluctuate between 40 and 80 depending on engine RPM. My guess is either someone has been in there, or a faulty gauge. The oil looks good, and when I had the valve covers off there wasn't a bit of sludge, so I figure all is well regardless of what the gauge says.

Steve :w

On my 72 LT-1, I get something very similar (not sure the exact numbers, but it maxes out at start up, then goes to mid-range when warm). Is this OK? Unlike sac001, I haven't checked the oil yet (had the car less than a month).
 
Joined
Aug 29, 2001
Messages
3,235
Location
Norcross, Georgia, United Stat
Corvette
2017 Arctic White Grand Sport
On a car I had when I was younger, ok I admit it was a VW, there was an oil pressure relief valve of some type. When you started the car cold, it produced max pressure at idle, and once it warmed, the valve kicked in and the pressure dropped at idle though at speed it was max again.

The bigger engines in the vettes seem to work on the same principle, though I don't know this for sure.

Bob
 
Joined
May 6, 2002
Messages
129
Location
Simi Valley, CA USA
Corvette
1975 Red on RED Coupe
The consensus seems to be that anything between 20 and 80 on the gauge is fine... Like Nut said and my buddy here (who mostly works on MGs) Its fine ....There's pressure.. that's a good thing
 
S

Stingray72

Guest
I have about 3000 miles on the rebuilt motor and my oil pressure never drops below 35 in any condition I've had it in yet. However, late model LT1s in mid-90s Camaros will maintain oil pressure at about 10 psi at idle, and this is normal according to the user manual.
 
Joined
May 29, 2002
Messages
8,653
Location
Missoura Ozarks
Corvette
2012 💯 4LT GS Roadster
Thicker oil holds higher pressure @ start-up . . .

After it's warm the pressure drops and then picks up as necessary @ higher RPM's
 
Joined
May 6, 2002
Messages
129
Location
Simi Valley, CA USA
Corvette
1975 Red on RED Coupe
A buddy of my suggested running 5w-40 ...I have 10w-30 in it now. Come to think of it that's a question to ask.. Heavier oil would in crease the pressure , right?
 

WhalePirot

Well-known member
Joined
May 9, 2002
Messages
2,942
Location
SoCA
Corvette
1984 White Z-51/ZF6-40/Shinoda body
When Mobil 1 first came out, their brochure stated that the oil was so slippery that 5 psi was okay at idle! I have NO idea if that is really true, or if their formulation has changed.
 

Nut

Well-known member
Joined
Oct 15, 2000
Messages
890
Location
Bowie, MD
Corvette
Vette-less for now
5 psi would give me a case of the hives!! I'd never stop watching the gauge everywhere I went. Seems hard to swallow that one, but I did see that in an article too.

............. Nut
 
P

page62

Guest
Use straight 30-weight oil. It's actually what Castrol recommends for your car in the warmer months!
 
W

wolf_walker

Guest
Anything other than a very recently rebuilt older V8 gets 20/50 in the summer for me, 10/40 in the winter if it shows signs of low pickup when cold starting, maybe lighter if your in a really dead cold climate.

I have an original 1978 Ford 460 that holds 30pis hot at idle and 55+ at highway speeds, with 214K miles on it.. :)

The vette with 120K runs about 20psi at idle hot and a little over 35psi on the highway.

Oil preasure specs for older cars are usually for a hot motor holding 2000rpm, fyi.. :)
 
J

jmp

Guest
gotta bring this up again...

...because I had a bit of a scare last night.

I was heading from work to my first corvette club (BCCC) meeting, when I noticed that my oil pressure gauge was reading lower than usual. While driving it was reading around 35 -- normally it's closer to 70. At idle, things were worse. Not only did the gauge drop to somewhere between 5 and 20, but the needle was also 'jumping' a bit (normal is around 35). But, as soon as I gave it gas, it went back up to 35.

And it got worse. By the time I was turning into the parking lot, the gauge was reading 30 while in gear, and 0 at idle! Needless, to say, I quickly shut the car down.

After the meeting I checked my oil levels. Empty. Considering I had checked the levels about 500 miles ago (and it was just under full), I fully expected to see oil everywhere. But I saw nothing. No puddles. Engine was clean and dry. Oil filter was fine.

So where'd my oil go? Do (older) 'vettes drink oil that fast? I'm not burning oil (no smell, no smoke). I had thought I'd be fine for 3000 miles, but I guess not.

Also, I bought new oil but by the time I got about 4 L (1 gallon) in the car, the dipstick read way past full. I thought the car took 5 L of oil? Maybe the dipstick is not the right one for my car?

[Edit] It just occurred to me that dipsticks may not be designed to show all the oil in the car, just when it gets lower than a certain point. So I could have had two litres in the car but the dipstick only shows the "top" 3 litres. Anyone know if this is the case for an LT-1?

Driving home I kept an eye on the gauge. It started off a 65/35 (driving/idle) but lowered to 55/20 by the time I got home. I rechecked the oil levels and it was roughly the same as when I started the trip (past full).
 

Jack

Well-known member
Joined
Dec 27, 2000
Messages
1,825
Location
Florence, SC (Timmonsville SC)
Corvette
71 War Bonnet Yellow VERT 71 BH Blue CPE (SOLD)
jmp:
The stock vette oil pan holds about four qts and the filter holds about one more qt for a total fill of about 5 qts. It's my experience that the stick APROXIMATELY measures "about" the final two (of 5) qts. So ... oil level could be just below the stick's tip and you could still have two qts in pan & one qt in filter.

DO NOT overfill the motor! That is ... do not operate it when overfilled. If it's overfull by more than say one-half qt ... DO drain the excess out. Overfilling can allow oil level to reach spinning crankshaft ... the crank will aerate the oil (NOT good for bearings/lifters & such) .... aeration can/will cause gage to jump around ... overfilling can cause oil to finds leaks that might not have been there before.

Suggestion: Go get 5 qts of good oil & a good filter ... and some aerosol engine degreaser. Clean off the engine and engine bay ... top to bottom .... and Drain & Change o&f. Before you screw on filter ... try to fill filter about 3/4 full with oil ... this takes a few minutes and several dollops as the filter wicks up the oil. Once filter is installed and plug is in pan then add 3 to 4 qts to engine. Then read the stick. Don't add more until you crank the engine ... verify you have steady pressure. Shut off motor and come back in ten minutes and read the stick ... then add the remainder. Then read the stick for final measurement. At this point you know you have 5 qts in it and it should show just full on stick. If not then you have wrong stick (some of the chrome aftermarket ones are mismarked) ... or a different/non-stock oil pan. Keep a close check on oil levels for a while. With a clean motor and known correct fill ... you can determine if there's a leak or whatever.

G'luck
JACK:gap
 

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