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low oil pressure


Let Them Eat Cake
Elite Explorer
May 13, 2000
Reaction score
City, State
Cape Girardeau, MO
Year, Model & Trim Level
94 Sport 4x4
My oil pressure still reads in the "normal" range on the gauge, but it has been hovering around the "n" or "o" in the gauge as opposed to the middle like it used to. I am running 5W-30. Shouldn't it be in the middle of the gauge?

I used to run 10W-30, but switched to 5W-30 at my last oil change. What are the possible causes of this change? Is it related to the weight of oil? Is it something with the sensor or computer? Is it the cooler weather? It's not leaking any oil at all, and the oil level reads normal on the dipstick.

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After reading a lot of old threads about oil pressure/sending unit/etc. I am thinking that maybe I should be using 10W-30 as opposed to 5W-30. My manual says 10W-30. I know some people's manuals say 5W-30 (the northern climates). I put 5W-30 in last time thinking it would be better if I do a camping trip to Wisconsin (last year it was -20F up there). However, since I have put in the 5W-30 I have had a little lower oil pressure. That's why I am thinking of just sticking with Mobil1 10W-30.

Oil Pressure

Yes, the tninner oil (5W-30) could defintely account for a slight drop in O.P., but...Ford says, at least in the manual for my '93, that anywhere in the normal range is O.K., so it's unlikely you're doing any damage. You only really need to worry if it drops below the normal range.

From what I've read on here (and heard from other people) the Oil Pressure guage is just a fancy idiot light. When the pressue drops below 5psi (I think it is 5) the guage reads very very low pressure.. anything higher and it shows in the normal range. There are a few threads on here about the "fake oil guage" and even instructions on how to convert it to a normal guage.


I would get a mechanical gauge and hook it up see what the actual pressure is. As you found out the gauge is nothing more than an idiot light in function. The gauge reads low when the pressure drops below about 7psi. I wouldnt be concerned about the gauge reading unless it swings all the way left.

I use an old mechanical gauge from Auto-Meter to run checks. Just remove the sender and screw it in - pretty easy to get to. I would then take it for a drive and note the pressures. Factory says 40-60 psi at 2000 rpms with the engine and oil hot. Mine runs at about 55psi hot @2000 rpm, and is around 30psi at idle.

Hope that helps.

Thks for the info. Now, can I buy such a pressure testing gauge at a place like AutoZone?

If so, I hope I can find the sending unit. Then, just unscrew the line, and hook it to the gauge? Once this is done, how can I read the gauge while I'm driving if it's under the hood?

You should be able to get them just about anywhere. Look for a mechanical oil pressure gauge 0-100psi - Sun, Autometer are some brands. The oil pressure sending unit is at the driverside front of the engine- it has one, single wire connection to it. Unscrew it, and replace it with the tube fitting for the gauge. Oil will come out when you remove the sender- but only a couple of ounces. There should be 5 or 6 feet of tubing, I ran the tubing up and out of the hood, taped the gauge to the cowl for testing. Not pretty but does the job.

Yeah... that's the way to check it.... I suspect everything's A-OK. a lower oil pressure isn't necessarily an indication of poor oil flow. Pressure is generated by the resistance to flow, and if you are running a slightly "thinner" oil, it will have less RESISTANCE to flow, and therefore less pressure built up at the sending unit.
Just my thoughts....