LOW oil pressure at hot idle
04-23-2012, 12:00 AM
#1
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LOW oil pressure at hot idle Guys,
I drove my car on the highway for an hour and was sitting in traffic and the check gauges light came on for the oil pressure. It's been hovering right above red at hot idle since a number of 13.2 @ 106 passes last month (caught it at low pressure after a run and shut it down). At 3k rpms the pressure is at 60psi. I just put in a 3200 converter about 1000 miles ago. I'm wondering if the decreased load on the motor at idle is causing it. I'm planning on bumping up idle from 600 to 850 to see if that helps. I'm running 5w 20 dino with lucas additive (the thick stuff) and plan to put in thicker oil asap. No unusual noises from the engine.
Info I've read: bearing tolerances increased (no clue how that happens / what it is), damaged oil pump, thin oil, gas in oil, etc.. I'm just a little on edge. Any help?
THANKS
Austin
I drove my car on the highway for an hour and was sitting in traffic and the check gauges light came on for the oil pressure. It's been hovering right above red at hot idle since a number of 13.2 @ 106 passes last month (caught it at low pressure after a run and shut it down). At 3k rpms the pressure is at 60psi. I just put in a 3200 converter about 1000 miles ago. I'm wondering if the decreased load on the motor at idle is causing it. I'm planning on bumping up idle from 600 to 850 to see if that helps. I'm running 5w 20 dino with lucas additive (the thick stuff) and plan to put in thicker oil asap. No unusual noises from the engine.
Info I've read: bearing tolerances increased (no clue how that happens / what it is), damaged oil pump, thin oil, gas in oil, etc.. I'm just a little on edge. Any help?
THANKS
Austin
04-23-2012, 01:12 AM
#2
Oil is too thin and Lucas is garbage.
People mistakenly think because its "thick" it will protect the bearings better, or hold better oil pressure.
In reality Lucas additive is terrible to foam up, and when it foams your oil pressure goes to ****...
Get rid of the snake oil, and use a quality 10-30 dyno oil, or a 15-40 diesel engine oil and see what the pressure does.
A quality oil filter is key here too. You want FLOW in a performance app, not only filtration.
I use K&N oil filters for this reason. In my experience they flow really well, as well as filter well.
People mistakenly think because its "thick" it will protect the bearings better, or hold better oil pressure.
In reality Lucas additive is terrible to foam up, and when it foams your oil pressure goes to ****...
Get rid of the snake oil, and use a quality 10-30 dyno oil, or a 15-40 diesel engine oil and see what the pressure does.
A quality oil filter is key here too. You want FLOW in a performance app, not only filtration.
I use K&N oil filters for this reason. In my experience they flow really well, as well as filter well.
04-23-2012, 11:25 AM
#6
The load on the engine shouldn't have any effect on the pressure. It's a the rpm's that drive the speed of the pump which results in the pressure at that point. A higher viscosity and higher rpm combination will give more pressure. I would think that 500rpm is a little low for idle speed personally, though I don't run an auto myself.
04-23-2012, 11:43 AM
#7
the definition of tolerance is the +/- amount from a given value you expect clearance to be or the range of values acceptable clearance can be.
the combination of 600 rpm which is quite low coupled with what was probably very hot oil temperature and 5w-20 oil resulted in low pressure. i would expect that. the fact that pressure goes to 60 psi on the 5w20 at high rpm means the oil pump is working and you don't have excessive bearing clearances. If you continue to run 5w20 oil, ensure that oil temp stays below 200F to maintain high enough viscosity and good enough oil pressure at low rpms, and/or keep idle rpms higher. Going from 600 rpm to 800 rpm at idle is a 33% increase in oil pump output and may fix a lot of it. But I would use a 30 weight oil, a 15w-40 is a better choice especially if you know you'll be sitting in traffic in hot weather because that's when the engine heat soaks and oil temps get up there.
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04-23-2012, 04:18 PM
#9
it's bearing clearance.
The definition of tolerance is the +/- amount from a given value you expect clearance to be or the range of values acceptable clearance can be.
The combination of 600 rpm which is quite low coupled with what was probably very hot oil temperature and 5w-20 oil resulted in low pressure. I would expect that. The fact that pressure goes to 60 psi on the 5w20 at high rpm means the oil pump is working and you don't have excessive bearing clearances. If you continue to run 5w20 oil, ensure that oil temp stays below 200f to maintain high enough viscosity and good enough oil pressure at low rpms, and/or keep idle rpms higher. Going from 600 rpm to 800 rpm at idle is a 33% increase in oil pump output and may fix a lot of it. But i would use a 30 weight oil, a 15w-40 is a better choice especially if you know you'll be sitting in traffic in hot weather because that's when the engine heat soaks and oil temps get up there.
The definition of tolerance is the +/- amount from a given value you expect clearance to be or the range of values acceptable clearance can be.
The combination of 600 rpm which is quite low coupled with what was probably very hot oil temperature and 5w-20 oil resulted in low pressure. I would expect that. The fact that pressure goes to 60 psi on the 5w20 at high rpm means the oil pump is working and you don't have excessive bearing clearances. If you continue to run 5w20 oil, ensure that oil temp stays below 200f to maintain high enough viscosity and good enough oil pressure at low rpms, and/or keep idle rpms higher. Going from 600 rpm to 800 rpm at idle is a 33% increase in oil pump output and may fix a lot of it. But i would use a 30 weight oil, a 15w-40 is a better choice especially if you know you'll be sitting in traffic in hot weather because that's when the engine heat soaks and oil temps get up there.
04-23-2012, 06:25 PM
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Second that! I'm almost wrapped up with a mech engineering degree, I enjoy thorough explanations. Pulled the tune and hot idle is 550 rpms in drive, 650 in neutral 
. Anyways, changed the idle to 725 in drive and 800 in idle. That should fix it with some thicker oil. I actually just sold it this weekend so I'm making sure everything is right before I can be at peace. I'll miss that car. Funny how my goal was to hit 12's and when I figured I could do it with better tires (2.2 short), I sell the car and buy a 99 SS 6 speed.. 
Thanks a bunch guys, I had a hunch about the idle and oil but I got myself worried up pretty good.
God Bless
Austin
. Anyways, changed the idle to 725 in drive and 800 in idle. That should fix it with some thicker oil. I actually just sold it this weekend so I'm making sure everything is right before I can be at peace. I'll miss that car. Funny how my goal was to hit 12's and when I figured I could do it with better tires (2.2 short), I sell the car and buy a 99 SS 6 speed.. Thanks a bunch guys, I had a hunch about the idle and oil but I got myself worried up pretty good.
God Bless
Austin
