The other day I had my 1978 Pace into the mechanic. My mechanic noted that my oil pressure gage read 40. He said for my vehicle that it should be nearer to 60. He told me that either my oil pressure gage and sending unit was broken, or that I shouldn't be expecting too many more miles on my engine.

It is an L-82 Engine, 63K original miles, and I run Kendell 20W-50 (non-synthethic) oil.

- Do others agree that the oil pressure gage for this car should be at 60?
- Have any others had this happen, is it work spending the $ to replace the gage?

FYI - I do not burn oil, there is no engine knock, the engine still has pleanty of performance. There are no direct signs that the engine is going out.


[Modified by freemyer, 10:04 PM 6/5/2003]

 

At what rpm was it reading 40? If it was at idle it's normal. Many new cars read much lower at idle. My 96 Z28 had 25 PSI at idle, for instance.

At higher rpm (about 2500) the pressure will be higher. I expect to see about 50 or so.

As long as the engine runs good and doesn't burn much oil or make funny noises, it's fine.

 

40 seems like normal oil pressure to me...

 

40 is plenty at idle. 5 lbs is enough at idle, but if the pressure does'nt rise to at least 40, then it's time to worry. sounds to me he is trying to sell you parts you dont't need. I have a high volume oil pump and mine is 40 at idle and it rises to 75. I have less then 200 miles on new motor. I would not worry about it.

:cheers: Larry

 

From what I recall, sitting here on my computer, it always runs near 40, no mater the RPM.

I (think) the only time I have seen it lower is near to 20, if the engine is idling with the transmission in neutral after the engine is warm.

I was more curious than actually worried about it. :D
Thanks for your input! :seeya


[Modified by freemyer, 10:24 PM 6/5/2003]


[Modified by freemyer, 10:25 PM 6/5/2003]

 

:iagree: mine stays at 40 at idle, at cruise it is always at least 65-70. :cool:

 

I have a 350 with a 291 Speed-Pro Cam and Hypereutectic Aluminum pistons, pulling about 400hp and, at idle (550 rpm), I'm show 40lb of oil pressure...when I'm cruising at 70-80mph, I showing 60lb of pressure....I use Castrol 20w40. :auto:

 

The owner's manual for my 1980 states, " Readings of 30 to 40 psi may be considered normal during moderate road speeds of 35 to 40 mph with the engine at proper operating temperature."

They also state that cold engines, hot engines, oil viscosity, outside air temperature, etc effect oil pressure.

Looks like you are ok.

 

Way back in '73 the Chevy standard was 40 psi at 2000 rpm.

tom...

 

Mine reads 40psi At idle at normal operating temp.Thats even in drive at 500rpms. Crusing I see a bit more around 60psi or so. But you have nothing to worry about. If you have 7psi or less at idle your going to need some work but 40psi is better than most vehicles out on the road today. I wouldn't be listening to your mechanic on this topic.

Also I forgot to add. You have a pressure relief valve that will try and regulate your oil pressure some. It is located under your oil filter. Usually that will show on the gauge when they go bad. Your oil pressure will
fluctuate.
[Modified by IRON WILL, 9:28 AM 6/6/2003]


[Modified by IRON WILL, 9:32 AM 6/6/2003]

 

Mine runs 50-60 cold, but drops to 40 when warm. Seems like most Vettes in my club run around 40. I have been told the real key with oil pressure is drastic change. If your car has always run at 40 its fine. If one day it drops from 40 to 20, you hae a problem.

 

I agree with all of the other posts, 40 at idle. Why are you running such a heavy oil? 10 W 30 should be fine for normal driving. I used 20 W 50 in my 77 Camaro race car but I wouldn't use it in my other cars.

 

No particular reason why I am running 20W-50, probably just ignorance. :eek: The previous owner used 10W-40 and told me to do the same. I used 10W-40 up until this spring. When I went to have my oil changed, they no longer stocked 10W-40... They recommended the 20W-50, so I went with it.

 

20w-50 won't hurt your engine. Its still going to run about the same oil pressure as it did with 10w-40. The 20w is alittle thicker and is better if your running higher RPMs. I just changed my gears in my vette to 3.73 and I run 3500RPMs going down the highway. I only use the car in warm weather. The 20w-50 helps especially when your running high rpms. If you look a your owners manual or a repair manual. 20w-50 can be used within a certain temperature range. I think its 40 degrees and up.

This comparrison is a bit off but think of a lawn mower they use 30w HD. They run a sustained high rpm, thats why they use it.

The theory now a days is to get the oil to the moving parts quicker, thus the reason most new cars are using 5w-30 or 10w-30. But the oil also drains off the parts quicker. The heavier oil will take alittle longer to get to those moving parts but it will also take longer to drain off of them. It all depends on the cars use. Daily driver with stock gears and normal use, you don't need the heavy oil. If it is modified lower rear gears, higher running rpms, etc, yeah a heavier oil is more suited to your needs. maybe this will help clear this up alittle. The best place to talk to is and engine shop, builder. They know about this stuff and will be able to give you a much better idea of what you need.

 

Iron Will: I have checked my owners manual, and I think it was 20degrees and up for 20W-50. It doesn't really matter, the car is my weekend cruiser, and I only run it on nice days. At startup, I always let the engine warm up before I run it hard. {I will change the oil out at the end of the season before winter sets in, so I won't have a problem with it freezing up.}

I have a 1978 Pace with a factory gears. The car is an automatic, so it runs failry high RPMs, 3000+, on the highway.

I think based upon your explaination the 20W-50 is probably better than the 10W-30 for me, being that I do not have startup concerns (being too cold, running it hard at startup) and the car runs fairly high RPMs on the highway...

 

I run the Valvoline VR1 Racing 20w-50 in my car. I have used it in all my small block cars. I run the car pretty hard for the most part. I change to 10w-40 in the winter for storage. There are some 20w-50 oils that are specifically for racing only aplications so check before you use them. I also only use AC delco oil filters. I currently use the part #PF454 which is a replacement part number for the old PF25. The oil I use in not a synthetic or a blend. I was told to break in the motor with conventional oil, and I could switch after but decided to run it on what it was crissoned with. You should not have any problems as I said before.

I am curious as to what the stock gears in that Vette of yours are. Mine were 3.08 stock and it didn't run more than 2500rpms at 65 if I remember right. If I was to guess I would say they are 3.42 or 3.55 gears. At any rate, enjoy the ride and don't worry about the 40psi oil pressure that sounds good to me especially if its at idle.

 

Something i read once, dont remember exactly where, said a good rule of thumb was to have 10 lbs of oil pressure, for every 1000 rpm's you plan on running for proper lubrication. My '80 runs at 40-50psi for the most part, but I've noticed it drop a few pounds right after i come off the freeway,
on a warm day. My guess is the oil is thinner, shrug, works fine.

 

First off you pressure sounds normal to me if the car still has the factory pump. Before I changed my pump on my 70k mile engine I had 25 at hot idle and 40 at cruise. Then I swithced to a high volume pump and I now have 35 at hot idle and 65-70 at cruise. So long as you stay below the factory redline for yur engine then 40psi is enough pressure.

Secondly, in your cooler climate I would recomend running a thinner oil. Protection is more about volume then it is pressure. With the thicker oil its harder for the pump to push the volume thru. I would strongly recomend Mobil1 synth 10/30 in yur climate. You may notice a slight drop in pressure but again, its more about volume, not pressure.

 

My oil pressure is around 70 :eek:

 

Mine too, what to check?

Correction, 40 psi at 600 rpm's, 70-80 at 2000 rpm's,


[Modified by 74 vert, 3:17 PM 6/7/2003]