20w50 too thick?????

Ok been having problems for awhile now with high oil pressure...im talking 70-80 psi constant. I put a new OPS in it say 5 months ago and I'm thinkin that maybe it went bad again....not likely but a possibility. Now another possibility is that maybe i should be running 10w30 as opposed to 20w50? My engine has 109K on it but still has great compression all across the board...the only reason i use 20w50 is b/c of the high mileage and I have no clue what the owner before me ran...does this sound like a valid arguement?

Not sure about that thick oil. I use 10w-30 on my 4.0 with 138k miles no problem. You might want to try a thinner oil. The thinnest oil you can run safely is the best.

Try checking the oil pressure with a mechanical gage. I doubt if the oil could be the cause but you probably don't need to run 20-50 in the Florida winter and with such low mileage. 10-30 should be just fine, maybe 20-50 in the summer. I believe the manufacturers like to specify the thinner oil (5-30) because it helps their CAFE average.

20W50 is too thick, but not for the reason you're describing. When cold, the oil will be a 20 weight, and in winter that's too thick to get good oil circulation when starting. Once the engine warms up, the oil will act like a 50 weight, but that's not a problem.

I run Castrol 5W50 in both my '88s. In the XJ with 240k miles, my normal running oil pressure is about 40, and 25 to 30 at idle. In the MJ with 110,000 on the clock, normal running oil pressure is about 55 to 60 psi and it idles at 30 to 35.

Those senders are notoriously inaccurate and short-lived. I think your sender is faulty.

;I agree with eagle, that the sender is suspect. Anyway, I would use thinner oil, the thinnest that can maintain adequate pressure. As long as it's viscous enough to keep the bearings cushioned, the thinner it is, the faster it will flow and take away heat (or so I am informed or misinformed....)

I have used 20w50 in my 89 XJ for the last 6 years with no issues. It has over 230k miles on it and still runs strong w/ +40 psi under power and +20 psi at idle. I use it in my 99 XJ as well. I get about 40 psi at idle and about 60 psi under heavy throttle.

I do agree with the too thick for winter, but I live in southern california and our winters are equal to most of the states summers. I can manage with my 20w50 JUST fine.

-Scott

20W50 is too thick, but not for the reason you're describing. When cold, the oil will be a 20 weight, and in winter that's too thick to get good oil circulation when starting. Once the engine warms up, the oil will act like a 50 weight, but that's not a problem.

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I would agree but this guy lives in Florida. I doubt they have much freezing weather there. Same with the guy who reported no problems (Cali).

The sending unit sounds funny to me as well.

I've used Mobil 1 20/50 here in Michigan for years, year round, without a problem (yet). The thick stuff takes the diesel out of the 4.0.

I run 20/50 synth w/no problem.

I run 20w-50 Royal purple synthetic in my '96 and my oil pressure is the same as when I used "natural" 10w-40 (previous owner) - around 40-50 psi.

Oil viscosities....always a 'hot topic'....no pun intended. Is interesting how fikle the viscosity ratings of oils are. The best way really know is to ck the real down and dirty specs for the specific brand you are using or are considering to use. I have found it varies quite dramatically.

Here is one example:

Eagle says he uses Castrol 5w-50 year round in his vehicles. I like to pretty much stick with a full 15w-50 Mobile 1, maybe dilute the 5 qt. jug with two 10w-30s if is heading into winter when doing the service. But going 10k miles min betw/ services would easily slide right back into the heat of summer before needing to change again..... I just like the increased 'cusioning' of that heavier wt oil. I have the feeling some of the clearances in these engines are best served with some oil help to make up the 'difference'.

To most properly consider the cold weather properties of these two oils is to look at the actual pour points. The 5w-50 Castrol has a pour point of -45, while the 15w-50 Mobile 1 has a -55 pour point!! In other words the 'thicker' Mobile 1 actually is better than the 'thinner' Castrol in really cold weather!! Some manufacturers seem to better rate their's at a "borderline pumping temperature" which seems to be about 20 degrees above pour point.

Kinda makes that viscosity rating listed on the cans not totally accurate and therefore not that valuable, doesn't it?

I have high oil pressure too. Usually run straight 20-50 but during jan-feb I might throw a quart or two of 10-40 in there to thin it out a bit. odo broke at 140k. The pump should have a pressure relief spring loaded vavle that keeps the pump from blowing the oil filter off, right? I usually have 60 lbs running down the highway.

-55 and -45 WTF is that? You northern exposure guys are nuts !!! I couldnt get that cold here if I stuck my head out the window of my xj on the interstate on the coldest day of the year.

My friend ran 20w50 in his YJ with a 4.0 and 140K. The engine didn't "sound" right when ever I listened to it and its owner complained about oil pressure. I told him to just try running 10w30 after a good motor flush. That took care of the low oil pressure.

I run M1 10w30 all year long and maintain 45psi hot/at speed, 25psi hot/idle.

--Matt

I lived in Tampa for 23 of my 30 years. Since I was 16 and had a car I always used 20w50. There are only around 5-10 days in the winter when the temp gets down near freezing. I never had any bad experiences with that weight oil. Its not uncommon to have temps in the high 70s to low 80s in the middle of "winter" in Tampa.

Also, the oil sending unit in XJ are junk. I'm on my third one. Last time it went bad the guage was reading 80 psi all the time.

Now that I'm in West Virginia I still run 20w50, May thru Oct. I switch to 10w40 the rest of the time.

I had a 89 Eliminator 2WD...loud ticking noise...146k miles or something...noisy lifter two back...not worth tearing down head to replace. Put in 20w50 and it's a little less noisy, but still noticable. No probs so far in the cold we've had.
Starts everytime, runs w/ great pulling power, oil pressure went down from pegged to 35-50 range with the 20w50.

I run 10w30 in all my vehicles, thinking about going to 10w40.

the 87 has 174k, the 90 has 107k

Teron

I use 10-50 synthetic, cranks OK, even when really cold ( "0" and below). Seemed to slow down a slow seep, in both ends of the crank. Raised my pressure about 5 PSI at operating temp. Does seem to hestitate, on the gauge a tick, before oil pressure comes up.
Try grounding your sending unit, as a test. I remember a recommendation, not to use thread sealer, when installing a new sensor. Many senders reguire a good ground to function properly. I´d try cleaning a couple of spots and holding a short jumper wire in there just to test the ground. Or maybe an ohm test between the sender case and ground. Some senders go all the way up, with poor contact, ground or open circuit. A dead short will make the needle go all the way down. Some are the opposite (can´t remeber off hand which is which). Unplug it and see what the needle does, if it goes all the way up, you may have a loose/corroded connection or a poor ground.