Ok so today my oil psi gauge started to fluctuate from 35-10 at stop lights. It stayed at a steady 45 while driving. Can this be a bad sender or something else?

 

Normal once you get up to operating temperature

 

Mine use to shoot all the way to 80. Replaced the oil pressure sending unit and it does the same thing yours does. So I'd say it's fine.

 

It stays at a constant 40 when it's cold. Then as it gets to op. temp is when it starts to fluctuate.

 

Anything >0 is usually OK.

 

It runs great for 274,000 except some ticks and other noises that iv been told are normal to. I'm new to the jeep world so I guess there's a lot I need to get use to with these 4.0s.

 

Fluctuation is normal on a vehicle that has a "live" oil-pressure gauge. Once the oil gets up to temp viscosity and pressure drop, when you accelerate engine RPM increases and the oil pump spins faster moving more oil which increases pressure.


Factory spec says a min of 13psi at hot idle, but the gauge isn't very accurate so if it is around 10psi you should be fine. If you are running a Fram (or other cheap / "off-brand") filter get rid of it, those things are junk and known for causing pressure issues. Wix/Napa Gold, Purolator, Motorcraft, Baldwin, Bosch, Mobil 1, etc. are all good brands of filters. If you have a 91 or newer you can also run an "oversized" filter (Motorcraft FL-1A, Purolator PL30001, WIX 51515/Napa 1515, etc.)which increases filter area and slightly increases oil capacity (aprox. 1/2 qt.).

 

We'll I am running a fram filter at the moment. As soon as I cash my check I'm picking up a good filter and some rotella t5 10-30. I was told to use rotella t6 5-40 but I don't want to run synthetic and I want to stick with what the engine calls for.

 

[QUOTE=dmill89;2803707

Factory spec says a min of 13psi at hot idle, .[/QUOTE]

That factory spec is for an engine in reasonably good condition...and not an engine with 300,000 miles. On a tired engine low pressure at idle is not uncommon. As long as it comes up with rpm all is well.

 

Well it's never dropped below the 10psi mark on the stock gauge at idle and alway comes right up between the 40 and 50 mark under throttle. I thinking of getting a good after market gauge it should be more accrued then the stock one. I'm thinking of getting one with a digital read out.

 

Just remember if you don't want to get a "check-gauges" light you need to leave the stock sender and install the aftermarket sender with a "T" fitting (so you will have 2 oil pressure senders).

 

Don't get too obsessed over oil pressure...it is the most mis-understood function on an engine with more opinions and myths than you can shake a stick at. This is the very reason Jeep eliminated oil pressure gauges starting in 2004 and up till now. Your pressure is fine...enjoy your ride!

 

My 2004 Grand Cherokee has an oil pressure gauge in it.

 

Ha.ha, you just THINK you do!

 

Get Rotella and a Wix/Napa Gold filter on there and see what happens first.

BTW, what year is your Jeep?