Disappearing oil

Redheadmedic

Redheadmedic

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Joined
Jan 15, 2022
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Richland, Wa
5 months ago, I got myself a screaming deal on a 93 YJ. It's been my dream vehicle for many years and when I found one with 150k miles, no major issues, well kept and in extremely good shape, manual trans, AND the color I wanted UNDER $5k, I knew I had found a unicorn! Now I'm not much of a car person. Actually that statement probably over sells my car knowledge considerably. I had my shift partner look it over and test drive it for me. He has considerable Jeep experience and when he approved, it was mine. I'm learning a lot. I do all the work on it myself under his direct supervision.
My baby has a new issue that has us scratching our heads. She's burned through 3 qts of oil in 3k miles. We climbed underneath and nothing. She's clean, no major leaks, no stains on my driveway, no notable oil anywhere. Looked all over the engine compartment, nothing new there either. Dipstick stays nicely seated. PCV is fairly clean. No oil in my radiator. Checked the spark plugs, (something about compression and/or worn rings, honestly I'm on information overload at this point) they all looked good. I'm not noticing any loss of power, no strange noises. It's just gone. Any advice for this newbie? I'm seriously lost.
 
Is it smoking at all when it runs?
If so, is it more pronounced under acceleration, or deceleration.
If it is smoking more when decelerating it's probably valve guides.
Not an easy job, but better than the alternative of a shot motor, and with yours at only 150K, I doubt that.
Does sure sound like a lot of oil usage for not marking it's spot.
 
We are going to do a leak down test, whatever that is 🤣 I presume that will tell him something and he will translate the info to me in words I understand?
 
PCV is clean? On my 2.5L there is no actual valve but instead there is a small brass fitting inside the valve cover that has a small hole for airflow. Mine was totally plugged and needed to be removed, cleaned, and re-installed. I think the 4.0L is the same.

You may find a higher oil consumption if yours is plugged.

Can anyone else verify this?
 
Mine isn't an actual valve either. Just a rubberized piece that is fitted on top of the valve cover. Both this piece and the hose running from it were fairly clean, meaning no sludgy gunky buildup.
 
A couple things for you to check. Look inside the airbox for a oil covered filter or oil everywhere. I cant recall what years specifically but there was a TSB to replace the crank vent lines. IIRC it either has that brass orface or a valve of sorts somewhere to regulate the flow. My 91's brass orface does get plugged up and I clear it with a small piece of wire thats the same size of the hole. DONT drill it out!, just clear the carbon. Secondly Im guessin 90% of the cars I see with a cloud of smoke behind has a clueless operator behind the wheel. I just dont think you can tell from behind the wheel. have your bud follow you when you drive it and run it good to see if he gets gassed out. Obviously if its not leaking its going somewhere and unfortunately its out the tailpipe.
 
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There is a white cloud of exhaust when it's cold, when it warms up, it is gone. I watched it in my rear view mirror this morning because right now I'm hyper aware of everything my jeep is doing. I admit, I didn't know anything about mechanics when I bought the Jeep but I'm quickly learning and have always watched my gages and listened to my engine to catch things quickly.
 
redbullet said:
I use this:

https://lucasoil.com/products/engine-oil-additives/high-mileage-oil-stabilizer
Click to expand...
Nothing personal here but Lucas products are like is K&N air filter in a can...garbage. Its nothing but uber weight wt oil with no additives just like STP or any other motor honey for 1/3 the cost. Modern lubricants are better now then ever and need no BS snake oil additives to make it "better" If you have a pile of crap vehicle ready to grenade then have at it. If you want a heavier oil use a 15/40 or 20/50 but be aware of temps where you live as it may be to much in cold weather.
 
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Gilaguy23 said:
Nothing personal here but Lucas products are like is K&N air filter in a can...garbage. Its nothing but uber weight wt oil with no additives just like STP or any other motor honey for 1/3 the cost. Modern lubricants are better now then ever and need no BS snake oil additives to make it "better" If you have a pile of crap vehicle ready to grenade then have at it. If you want a heavier oil use a 15/40 or 20/50 but be aware of temps where you live as it may be to much in cold weather.
Click to expand...
That’s right. There was a truck that I had that would burn 3 qts of 10w40 in 100 miles, and I could not see it behind me, or could others following me. But they sure could smell it. I was down to running Valvoline 50wt racing oil WITH STP, and that dropped the usage to 1 qt per 100 miles. But that wasn’t fixing anything, just a stop gap measure.
 
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I'd still pull the valve cover off and see what scary sights there are. That little brass fitting with an orifice probably can't be cleaned with spray cleaner or any additive due to the way it's hidden inside. As I recall it was hidden inside or under one of those towers you'll find on the inside of the cover. Mine was caked with a baked on layer of crud.

Generally, higher crankcase pressures will cause more oil to get sucked into the valve guides.

I used a good Felpro gasket. The previous owner used a full tube of silicone and made quite a mess and if not done right can clog your oil passages.
 
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Redheadmedic said:
We are going to do a leak down test, whatever that is 🤣 I presume that will tell him something and he will translate the info to me in words I understand?
Click to expand...
A bit of a long video, but I found his explanation of a compression test/ leak down test pretty good. Let me know how yall's go. I have the same situation with disappearing oil as well. I may try a synthetic 10W40 over the 10W30 I have been using. I have low compression in my 6th cyl. I have been meaning to do a leak down test, but would like to do it myself and still need to buy one.

Leak down test how to/ explanation:
 
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Gilaguy23 said:
A couple things for you to check. Look inside the airbox for a oil covered filter or oil everywhere. I cant recall what years specifically but there was a TSB to replace the crank vent lines. IIRC it either has that brass orface or a valve of sorts somewhere to regulate the flow. My 91's brass orface does get plugged up and I clear it with a small piece of wire thats the same size of the hole. DONT drill it out!, just clear the carbon. Secondly Im guessin 90% of the cars I see with a cloud of smoke behind has a clueless operator behind the wheel. I just dont think you can tell from behind the wheel. have your bud follow you when you drive it and run it good to see if he gets gassed out. Obviously if its not leaking its going somewhere and unfortunately its out the tailpipe.
Click to expand...
How often do you clean that little brass fitting? Mine was clogged pretty bad, cleaned it out and I'm hoping that fixes the problem.
 
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Cleaned out that little brass thing, hoping that was the issue. Air filter did have some oil on it, cleaned out the box and hoses. We shall see! Did a compression test, all cylinders between 135 and 150, nothing weird there. It sounds pretty and seems to have a tiny bit more power now.
 
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I hope it works. I don't know if there's actually a time schedule to clean it but it will remain clean longer with regular oil changes. Oil today is far cleaner and better than oil in the 90's.
 
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Ive put 10K miles but a bit of slow running time on trails on my 91 in the years Ive owned it and have done the clean 3 times. I seem to get oily residue around the oil cap when its time. I also take off the plastic hose and blow it out and if/when it gets to plugged up I'll replace it with some quality Vac line compatible with vapors etc. I change my oil every 2500 or when it looks crappy and use about 1/2 qt in that time.
 
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Gilaguy23 said:
Ive put 10K miles but a bit of slow running time on trails on my 91 in the years Ive owned it and have done the clean 3 times. I seem to get oily residue around the oil cap when its time. I also take off the plastic hose and blow it out and if/when it gets to plugged up I'll replace it with some quality Vac line compatible with vapors etc. I change my oil every 2500 or when it looks crappy and use about 1/2 qt in that time.
Click to expand...
My Jeep runs so few miles and idles most of the time when it does, I've been looking into hour-meters.
Like the kind they use to service heavy equipment....Just a thought.
 
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