oil pressures and oil weight
09-10-2017, 06:19 PM
#1
Racer
Thread Starter
oil pressures and oil weight
Here we go again.
I have read a lot the last several day about low oil pressure readings at operating temp idle and oil weights. A lot of the suggestions say to up one level in oil, from 5w30 to 10w30. Ok.... The way I understand multi grade, multi viscosity or W oils, the 5w, 10w, 15w etc reference the way the oil behaves when cold, and the last number, 20, 30, 40 etc reference the way the oil behaves at operating temperature or 100C. If all of that is correct, how does changing from 5w30 to 10w30 help warm, operating temp oil pressures? Most engine damage occurs at start up, so will to 10w get to the bearings and other necessary parts as it should? On the other end of the oil number, 20, 30, 40 etc, will the heavier oil provide a thicker layer of film between bearings and crank than the thinner oils? Thus providing better protection on a high mileage engine where bearing could be beyond original tolerances.
I have questions about my oil pressure. With a coolant temp of 195 - 200F, oil temp of 185 - 190F and highway speed or approximately 1500RPM, my oil pressure gauge reads nearly 40 PSI. At idle with same numbers, pressure will read 15 - 20 PSI. At cold start up, my oil pressure reads BETWEEN 40 and 60, regardless of RPM.
I have always been told by engine guys that when you oil pressure starts to jump when you close the throttle and then settle, you have crankshaft bearing wear. My gauge does this. I have ordered and new GM oil pressure sending unit. Prior to putting it in, I will use a manual gauge to check cold and hot oil pressure.
I have read a lot the last several day about low oil pressure readings at operating temp idle and oil weights. A lot of the suggestions say to up one level in oil, from 5w30 to 10w30. Ok.... The way I understand multi grade, multi viscosity or W oils, the 5w, 10w, 15w etc reference the way the oil behaves when cold, and the last number, 20, 30, 40 etc reference the way the oil behaves at operating temperature or 100C. If all of that is correct, how does changing from 5w30 to 10w30 help warm, operating temp oil pressures? Most engine damage occurs at start up, so will to 10w get to the bearings and other necessary parts as it should? On the other end of the oil number, 20, 30, 40 etc, will the heavier oil provide a thicker layer of film between bearings and crank than the thinner oils? Thus providing better protection on a high mileage engine where bearing could be beyond original tolerances. I have questions about my oil pressure. With a coolant temp of 195 - 200F, oil temp of 185 - 190F and highway speed or approximately 1500RPM, my oil pressure gauge reads nearly 40 PSI. At idle with same numbers, pressure will read 15 - 20 PSI. At cold start up, my oil pressure reads BETWEEN 40 and 60, regardless of RPM.
I have always been told by engine guys that when you oil pressure starts to jump when you close the throttle and then settle, you have crankshaft bearing wear. My gauge does this. I have ordered and new GM oil pressure sending unit. Prior to putting it in, I will use a manual gauge to check cold and hot oil pressure.
09-10-2017, 08:09 PM
#3
Melting Slicks
Here we go again. I have read a lot the last several day about low oil pressure readings at operating temp idle and oil weights. A lot of the suggestions say to up one level in oil, from 5w30 to 10w30. Ok.... The way I understand multi grade, multi viscosity or W oils, the 5w, 10w, 15w etc reference the way the oil behaves when cold, and the last number, 20, 30, 40 etc reference the way the oil behaves at operating temperature or 100C. If all of that is correct, how does changing from 5w30 to 10w30 help warm, operating temp oil pressures? Most engine damage occurs at start up, so will to 10w get to the bearings and other necessary parts as it should? On the other end of the oil number, 20, 30, 40 etc, will the heavier oil provide a thicker layer of film between bearings and crank than the thinner oils? Thus providing better protection on a high mileage engine where bearing could be beyond original tolerances.
I have questions about my oil pressure. With a coolant temp of 195 - 200F, oil temp of 185 - 190F and highway speed or approximately 1500RPM, my oil pressure gauge reads nearly 40 PSI. At idle with same numbers, pressure will read 15 - 20 PSI. At cold start up, my oil pressure reads BETWEEN 40 and 60, regardless of RPM.
I have always been told by engine guys that when you oil pressure starts to jump when you close the throttle and then settle, you have crankshaft bearing wear. My gauge does this. I have ordered and new GM oil pressure sending unit. Prior to putting it in, I will use a manual gauge to check cold and hot oil pressure.
I have read a lot the last several day about low oil pressure readings at operating temp idle and oil weights. A lot of the suggestions say to up one level in oil, from 5w30 to 10w30. Ok.... The way I understand multi grade, multi viscosity or W oils, the 5w, 10w, 15w etc reference the way the oil behaves when cold, and the last number, 20, 30, 40 etc reference the way the oil behaves at operating temperature or 100C. If all of that is correct, how does changing from 5w30 to 10w30 help warm, operating temp oil pressures? Most engine damage occurs at start up, so will to 10w get to the bearings and other necessary parts as it should? On the other end of the oil number, 20, 30, 40 etc, will the heavier oil provide a thicker layer of film between bearings and crank than the thinner oils? Thus providing better protection on a high mileage engine where bearing could be beyond original tolerances. I have questions about my oil pressure. With a coolant temp of 195 - 200F, oil temp of 185 - 190F and highway speed or approximately 1500RPM, my oil pressure gauge reads nearly 40 PSI. At idle with same numbers, pressure will read 15 - 20 PSI. At cold start up, my oil pressure reads BETWEEN 40 and 60, regardless of RPM.
I have always been told by engine guys that when you oil pressure starts to jump when you close the throttle and then settle, you have crankshaft bearing wear. My gauge does this. I have ordered and new GM oil pressure sending unit. Prior to putting it in, I will use a manual gauge to check cold and hot oil pressure.
What year is the car /engine?
The usual oil pressure requirement is 10 psi for every 1,000 rpm, if you are worried you can always fit a high volume oil pump.
That is what I did when I went to full synthetic oil, which dropped the oil pressure quite a bit at idle.
Note you will also need a heavy duty oil pump drive shaft on distributor drive oil pumps in 84-91 engines.
I suspect you may be talking about an LT1 engine?
Last edited by gerardvg; 09-10-2017 at 08:10 PM.
09-10-2017, 09:50 PM
#4
Racer
Thread Starter
Hi
What year is the car /engine?
The usual oil pressure requirement is 10 psi for every 1,000 rpm, if you are worried you can always fit a high volume oil pump.
That is what I did when I went to full synthetic oil, which dropped the oil pressure quite a bit at idle.
Note you will also need a heavy duty oil pump drive shaft on distributor drive oil pumps in 84-91 engines.
I suspect you may be talking about an LT1 engine?
What year is the car /engine?
The usual oil pressure requirement is 10 psi for every 1,000 rpm, if you are worried you can always fit a high volume oil pump.
That is what I did when I went to full synthetic oil, which dropped the oil pressure quite a bit at idle.
Note you will also need a heavy duty oil pump drive shaft on distributor drive oil pumps in 84-91 engines.
I suspect you may be talking about an LT1 engine?
09-11-2017, 09:02 AM
#5
Le Mans Master
Your engine oil pressures sound like a normal good engine.
I have the same opinions as you stated about oil pressures vs oil grades vs temperature.
I am not sure what you are describing about engine guys stating a pressure jump and then stabilize when the throttle is closed as a symptom of bad bearings. However, if the bearings are badly worn you will see reduced oil pressure especially when warmed up, and you may hear knocking from the excessive clearance. Since you don't mention either of these symptoms and your oil pressures are normal, I suspect that you don't have bearing problems.
Good luck.
I have the same opinions as you stated about oil pressures vs oil grades vs temperature.
I am not sure what you are describing about engine guys stating a pressure jump and then stabilize when the throttle is closed as a symptom of bad bearings. However, if the bearings are badly worn you will see reduced oil pressure especially when warmed up, and you may hear knocking from the excessive clearance. Since you don't mention either of these symptoms and your oil pressures are normal, I suspect that you don't have bearing problems.
Good luck.
09-11-2017, 11:42 AM
#8
Drifting
Why not just use what GM recommended; usually on the fill cap and owners manual. Vette L98 engines were not recommended for synthetic oil as an example. I don't fathom why owners of these engines think they know more than GM engineering, use it and then complain about oil leaks.JM2C
09-11-2017, 02:02 PM
#9
I use 0W-40 in my Porsche Cayenne, because that's what Porsche specs for it.
I use 10W-30 in my L98, because that's what GM specs for it.
I use 0W-20 in my lady friend's Honda, because that's what Honda specs for it.
I put straight 30 in the neighbor's 911 that I service, because that's what the book says to put in it.
See a trend? I make exceptions to using the recommended grades in certain engines and applications, but these are based on empirical evidence over years of observation and experience. When I don't have good reason to deviate from manufacturer's recommendations, I don't.
I use 10W-30 in my L98, because that's what GM specs for it.
I use 0W-20 in my lady friend's Honda, because that's what Honda specs for it.
I put straight 30 in the neighbor's 911 that I service, because that's what the book says to put in it.
See a trend? I make exceptions to using the recommended grades in certain engines and applications, but these are based on empirical evidence over years of observation and experience. When I don't have good reason to deviate from manufacturer's recommendations, I don't.
on my 87's oil cap, it says 5w30. perhaps my cap is from a different car but i have always wondered about the 5w30 it says. when i was younger working at gas stations it seemed like all cars took 10w30.
09-11-2017, 02:43 PM
#10
Le Mans Master
Your pressures are fine.. I only had 32 lbs pressure on my 89 at 1500 rpms and 15 lbs at idle and drove the car for 6 years like that.. The guy that has that motor now is still driving it in his car and it runs fine ,I went to a 383 engine instead..Going to a higher weight oil will not provide better oiling, it will just look like it showing higher oil pressure on the gauge. What's really happening with higher weight oil is , it's not flowing through the engine as quickly because it's thicker , this causes backpressure which shows as higher oil pressure. The lighter weight oil will actually give better lubrication then the thicker oil.. ....WW
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Last edited by WW7; 09-11-2017 at 07:51 PM.
09-11-2017, 06:33 PM
#12
Le Mans Master
Why not just use what GM recommended; usually on the fill cap and owners manual. Vette L98 engines were not recommended for synthetic oil as an example. I don't fathom why owners of these engines think they know more than GM engineering, use it and then complain about oil leaks.JM2C
09-11-2017, 08:21 PM
#13
Melting Slicks
Why not just use what GM recommended; usually on the fill cap and owners manual. Vette L98 engines were not recommended for synthetic oil as an example. I don't fathom why owners of these engines think they know more than GM engineering, use it and then complain about oil leaks.JM2C
BTW I have never, ever, ever seen a leak develop from using synthetic oil in an older motor. Ive put 9k on my L98 in 6 months using Mobil 1 0w-40 going through deserts, mountains, plains, and city driving. Guess what my 31 year old engine hasn't developed a leak yet.
09-11-2017, 08:23 PM
#14
Race Director
[QUOTE=ihatebarkingdogs;1595549058]
I use 10W-30 in my L98, because that's what GM specs for it.
QUOTE]
Where do you get 10-30?
OP, your motor is fine.
I use 10W-30 in my L98, because that's what GM specs for it.
QUOTE]
Where do you get 10-30?
OP, your motor is fine.
09-12-2017, 12:17 AM
#16
Melting Slicks
Even with the engine in the car, dropping the oil pan and rolling in a new set of crankshaft bearings isn't difficult
09-13-2017, 04:37 PM
#17
Le Mans Master
GM Engineering biggest priority..........EPA.
BTW I have never, ever, ever seen a leak develop from using synthetic oil in an older motor. Ive put 9k on my L98 in 6 months using Mobil 1 0w-40 going through deserts, mountains, plains, and city driving. Guess what my 31 year old engine hasn't developed a leak yet.
BTW I have never, ever, ever seen a leak develop from using synthetic oil in an older motor. Ive put 9k on my L98 in 6 months using Mobil 1 0w-40 going through deserts, mountains, plains, and city driving. Guess what my 31 year old engine hasn't developed a leak yet.
Last edited by Cruisinfanatic; 09-13-2017 at 04:38 PM.
09-13-2017, 04:52 PM
#18
Melting Slicks
Here's my other car its 46 years old and never had the valve cover off in its life I run synthetic in it (Amsoil Z Rod) and it doesn't leak either.
09-13-2017, 05:13 PM
#19
Le Mans Master
6 months in your vette isn't much of a test
