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Old 06-24-2013, 04:26 PM   #1
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Oil grade and pressure question

I was wondering if anyone else has similar experience with my 2004 Rubi L6 automatic. I bought it used with 86k miles. Had issues with oil pressure soon after I bought it. When running for a while, pressure would drop and dash worming light and alarm went on. Changed sensor and also found out dash was an idiot gage. Anything over 6psi shows mid scale, below shows zero. I had a mechanical gauge installed and switched from 5/30 to 10/30. Happened less frequent but still happened. I tried 10/40 with better results and also tried 15/40 (diesel engine recommended weight for German imports). With all oil levels the engine seems to react properly. Top oil pressure about 70 psi at 2800 RPM's. drops proportional to RPM's. with 15/40 a bit higher than 70 at 3000RPM. Lowest pressure with 15/40 is running about 15 psi. Specs call for lower level to be 13 psi's but gages allow down to 6 before you would know. Is there any reason not to run the 15/40 weight oil? Probably would run something lighter in the winter in New England. Any opinions would be appreciated.
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Old 06-24-2013, 04:32 PM   #2
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If you changed the oil pressure sender with something other than one from the dealer then I would replace it with an OEM. Aftermarket electrical parts are cheaper because they most likely come from chins and are usually crap. You get what you par for. Mine died a few years ago and replaced it with an OEM one and it is trill good as new after 120k.

Retired my 94 YJ 4cyl 5spd @ 200K
Now in a 04 TJ 4cyl 5spd CV @120K+
Both as a commuter vehicle in NW, NJ
April 2012.downsized and now a 99er.
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Old 06-24-2013, 04:35 PM   #3
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Raising oil pressure by running a heavier than specified viscosity is like eating donuts & hamburgers to raise an abnormally low blood pressure.

70 psi at 2800 rpms is much higher than is good & that is strictly from running an oil that is simply much harder to pump... artificially raising the oil pressure. In other words, an abnormally high oil pressure is no better than high blood pressure is... the goal should be simply to have good circulation. A good rule of thumb for acceptable oil pressure is roughly 10 psi per thousand rpms. Have a mechanic check it out, maybe your oil pump simply needs to be replaced to increase your low rpm oil pressure a tad.
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Old 06-24-2013, 04:45 PM   #4
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I got the sender from Jeep dealer. So how low a drop in oil pressure is Ok? 5 psi at 650 RPM at oper temp OK? I used the engine spec but if the gage accepts 6 psi as Ok, am I just being over critical about the lower pressure levels?
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Old 06-24-2013, 06:28 PM   #5
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I'm almost positive the factory low end spec is 13psi @ 900 rpm warm. Anything under 10 psi at idle is reason for concern and lifters start collapsing/ticking.
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Old 06-24-2013, 08:13 PM   #6
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I had questions about my oil pressure also.
my jeep runs around 40-70 psi.
40 when warm
60 at startup and about 70 on the highway.
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Old 06-25-2013, 02:12 PM   #7
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The jeep has never had any low engine oil noises like lifter clatter. The spec is 13 psi at 900RPM, I think your right. My jeep runs usually runs at about 700 RPMs. At this level, oil pressure with 10/30 oil would be acceptable probably 10 RPMs. But sometimes when run for a bit at warm temperatures, the RPMs would drop down to about 600-650. This is when the oil pressure would drop down to the 5 psi level and set off the alarms. Nothing worse that coming to a stop light and watching your oil pressure gage go to zero( idot light zero). Maybe this is fine and the issue is low RPMs. So I went to 10/30 oil. Problem is that folks aren't carrying 10/30 here anymore. So it's 5/30 or 15/40. I went to the parts store and got 10/40 and that's what I have been running. Not sure I need to crack open the engine for an oil pump change, but want this Jeep to last a bunch of years.

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