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Old 10-14-2010, 08:07 AM   #1
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Oil pressure drop at idle

I have a 2000 TJ 4.0 Manual with 135XXX.
When starting cold the oil pressure shoots up to 40 at idle and holds.
On the highway it will go up to 45-50. When warm after being on the highway when I come to a stop at a light it can drop to as low as 20 but typically 25-30. Ive had the Jeep for two years but just noticed this a few months ago bucause the steeing wheel covers the oil gauge from my vantage point when driving. I only have 60 miles on my latest oil change. As always I used 10w30 and changed filters.

Is this anything to worry about? Is this normal or is it a sign of bad things to come?

I should note there is nothing wrong with the Jeep that I know of. It runs smooth. This is also the first vheicle Ive ever had with an oil pressure gauge so I really have no frame of refrence here.

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Old 10-14-2010, 08:14 AM   #2
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Nothing to worry about, your Jeep is fine.

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Old 10-14-2010, 10:49 AM   #3
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Mine does the same thing at idle it's around 10or so hot and at hwy speed it's only 20 or so hot, but I'm gonna keep on driving, still runs ok
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Old 10-14-2010, 10:55 AM   #4
Knows a couple things...

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It is normal for oil pressure to vary up and down due to oil temperature and engine rpms. The oil pump is mechanically driven so oil pressure stays in step with engine rpms. Lower oil pressure at lower rpms, higher oil pressure at higher rpms. And cold engine oil is harder to pump than warm oil is so it is normal to have slightly higher oil pressure when the engine is cold.

The rule of thumb for acceptable oil pressure is approx. 10 psi per thousand engine rpms. That said, Jeeps newer than yours don't even show the true oil pressure any more. The normal ups and downs of oil pressure alarmed too many who were new to a true oil pressure gauge who complained to their dealerships. Jeep solved the problem of people unnecessarily complaining to their dealers about oil pressure variations by making the oil pressure gauge stay mid-scale except when something was really wrong with the oil pressure.
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Old 10-14-2010, 10:58 AM   #5
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My 98 does the same thing. I was worried at first and then I read the part on the owners manual about the pressure gauge and found out this is normal. I think if something goes wrong it will beep and illuminate the CHECK GUAGES light like it does for the low fuel light.
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Old 10-14-2010, 11:32 AM   #6
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NTW......(not to worry) unless it goes to zero......
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Old 10-14-2010, 12:12 PM   #7
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Quote:
Originally Posted by OregonTJ View Post
NTW......(not to worry) unless it goes to zero......
And if it goes to zero or pegs to max chances are your sending unit is no good, it's a jeep thing.
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Old 10-14-2010, 01:02 PM   #8
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Thanks all,
Just wanted to make sure that was normal.
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Old 10-14-2010, 01:04 PM   #9
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My jeep did the same thing and I changed the sender switch and it was hasn't done it since but it was going to zero so I needed to

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