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post #1 of 7 (permalink) Old 12-22-2004, 14:35 Thread Starter
Chasing down oil leaks...
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Low oil pressure - thicker oil?

I've put a S pac cluster in my car ages ago and only finally got around to putting in a oil sender for the gauge last week.

Went to the wreckers and got a sender with the intention of doing it at the same time as an oil change. Now I generally run Shell Helix 15W/50 (blue), but this time I got the lower spec 20W/50 Helix (yellow), mainly because it comes in a 6L bottle instead of 5L.

Anyway installed the sender and it didn't work. Was heading out west to work for a week so I stopped in at the wreckers on the way to get another one, let it cool down for 5 mins and then changed it still quite warm. At least the CFI manifold makes it a reasonably burn free job LOL..

The second one worked. Anyway for the question...

With the 20W/50 oil, at cold the pressure reads 3/7 (gauge reads from 0 to 7) which I think is good. As the oil heats up the pressure drops down to 2/7 when above 1500rpm, and below 1500rpm to idle, sits just under 1/7, which for my liking is too low. Also a slight rattle is noticable at the low pressure/low reading (which makes me believe the gauge is reasonably accurate), but its not low enough for the light to come on.

Now if I ran a thicker oil such as 20W/60 or something, I am assuming that the hot oil pressure will be higher. Maybe my oil pump is getting long in the tooth. How thick oil can a oil pump handle before you get problems? I see that Shell makes a 25W/70 oil that they call Sport or something.

Any suggestions? Filter is a purolator btw and oil was flushed with Nulon flush before change. Oil is brand new. Engine is 3.9L CFI.


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post #2 of 7 (permalink) Old 12-22-2004, 23:02
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Re: Low oil pressure - thicker oil?

Trouble with using a thicker oil is the lifters may get a bit noisy - at least this has been my experience. I doubt the pump is to blame for your low oil pressure - it's more likely wear in the crank/rods. If I were you I'd get the pressure checked with a proper gauge. My XF showed low pressure at idle, sometimes 1 bar (as in 14PSI) on the gauge, but in reality it was in specification when tested with a proper pressure gauge. In short, don't rely on senders.
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post #3 of 7 (permalink) Old 12-22-2004, 23:13
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Re: Low oil pressure - thicker oil?

hah, mine starts off at about 3/7 when cold, then goes down to 0/7 when hot.

Lifters aren't making any noise so I just leave it.
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post #4 of 7 (permalink) Old 12-22-2004, 23:15
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Re: Low oil pressure - thicker oil?

i have the same prob in the XF. at idle, when warm, i get the red bars flashing sometimes and when im cruising down the highway for a bit it goes right off the other end of the scale and starts flashing again but then comes back down and then goes back up....so forth and so forth.
i dont know and honestly dont really pay much attention to it any more.

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post #5 of 7 (permalink) Old 12-22-2004, 23:33
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Re: Low oil pressure - thicker oil?

my EB XR6 that i had with near 400000kays had lifter noise with 20w50 changed to 25w50 and noise went away, from memory oil pressure was ok never as low as you say but if they are similar to the ones in my XE the senders vary a little, i've got about 5 of them and they all read different. if the light didn't come on i wouldn't worry about it personally(providing the light works) but then again i reckon cahanging the motor is easy enough(ask me again when i have to change a motor again and i may change my opinion)
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post #6 of 7 (permalink) Old 12-23-2004, 00:03
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Re: Low oil pressure - thicker oil?

well my xr is the opposite , the oil pressure sometimes read 7 on the indicator while crusing the freeway, but not a regular thing - running hpr 15

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post #7 of 7 (permalink) Old 12-23-2004, 00:34
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Re: Low oil pressure - thicker oil?

I'm pretty sure I've got Shell 20W/50.
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