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Old 11-05-2013, 07:22 PM   #1
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JK using oil

I have an 08 jk. It does not leak any oil and does not smoke when cranking or running, but it seems to be losing oil somewhere. I have tried synthetic 5w 20. as recommended. Is the oil to thin and do I maybe need to use heavier oil? It only has 90k on it and its a daily driver. Seems like its losing a quart about every 1000 miles.

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Old 11-05-2013, 08:29 PM   #2
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I have an 08 jk. It does not leak any oil and does not smoke when cranking or running, but it seems to be losing oil somewhere. I have tried synthetic 5w 20. as recommended. Is the oil to thin and do I maybe need to use heavier oil? It only has 90k on it and its a daily driver. Seems like its losing a quart about every 1000 miles.
Suck some seafoam up through the brake booster vacuum line. You can find a procedure for this online. Then pour some seafoam into the motor oil and drive it for 50-100 miles. Drain oil and fill with 10w-30 oil. The oil loss is common on the 3.8 motor. This procedure took mine from a quart every 1000 miles to a quart every 5000 which is when I change synthetic oil.

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Old 11-06-2013, 05:45 PM   #3
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Why do you put in the vacuum line?
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Old 11-06-2013, 06:31 PM   #4
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Why do you put in the vacuum line?
You should Google it for lots of interesting reading. Basically there is most likely carbon build up on the piston rings that allow for oil to enter the cylinder in small amounts and be burned of without enough at once to see any smoke. Putting it into the vacuum line takes it straight to the cylinder to burn some of the carbon out. In the crankcase it thins out the oil to sort of de-sludge the motor. This process was published in a magazine for either 4x4 or jeeps specifically. There's a thread on here about it but I can't post the link from my phone. Be sure to read up before you put it through the vacuum hose as there is a specific process, if you do it too fast you can hydrolock the motor. There's some YouTube videos too.
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Old 11-06-2013, 07:59 PM   #5
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Go to 5W30 and replace the PCV. That has solved the problem with many 3.8's.
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Old 11-06-2013, 08:30 PM   #6
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I have an 08 jk. It does not leak any oil and does not smoke when cranking or running, but it seems to be losing oil somewhere. I have tried synthetic 5w 20. as recommended. Is the oil to thin and do I maybe need to use heavier oil? It only has 90k on it and its a daily driver. Seems like its losing a quart about every 1000 miles.
Mine burns MASSIVE amounts of oil if I run synthetic, or even a blend. Straight conventional oil gives me the best results.
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Old 11-06-2013, 08:44 PM   #7
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Stupid question, What does PCV stand for.
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Old 11-06-2013, 08:47 PM   #8
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Stupid question, What does PCV stand for.

PCV=Positive Crankcase Ventilation.
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Old 11-06-2013, 09:07 PM   #9
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Thanks for the help guys, I will try your recommendations. Still a little confused on the pcv. Is that a major fix? never heard of it.
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Old 11-06-2013, 09:46 PM   #10
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Thanks for the help guys, I will try your recommendations. Still a little confused on the pcv. Is that a major fix? never heard of it.
It's a tiny one-way valve that allows for crankcase ventilation. Every car for the last 20 years has had one. It's right on top of the engine.
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Old 11-06-2013, 10:02 PM   #11
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It's a tiny one-way valve that allows for crankcase ventilation. Every car for the last 20 years has had one. It's right on top of the engine.

They originated in WW2 for tanks to conduct river fording operations. They kept water out of the engine.

They go back to 1961 in California and 1964 in NY State for automobiles. The other 48 States came soon after and the valve allows the small amount of blow-by to get recycled back into the combustion chamber and get burned instead of being simply vented off into the outside atmosphere.
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Old 11-07-2013, 07:08 AM   #12
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Thanks for the help guys, I will try your recommendations. Still a little confused on the pcv. Is that a major fix? never heard of it.
At 90,000 I would replace it. You can get one most likely at any parts store or the dealer. Could be a little bit of a pain to remove, but you can muscle it out. Pull out the old one, push in the new one. They do get clogged. Additional info: It's behind the coil pack on the driver's side valve cover. Use a needle nose or channel locks to twist and pull straight out. It will come out you just have to coax it.
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Old 11-07-2013, 09:54 AM   #13
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At 90,000 I would replace it. You can get one most likely at any parts store or the dealer. Could be a little bit of a pain to remove, but you can muscle it out. Pull out the old one, push in the new one. They do get clogged. Additional info: It's behind the coil pack on the driver's side valve cover. Use a needle nose or channel locks to twist and pull straight out. It will come out you just have to coax it.
I would probably not use an aftermarket PCV. Many are not made to the right tolerances and can actually make problems worse. My Ford truck does not like anything other than a OEM PCV valve or it uses oil. If you are going to replace the one on your Jeep get a Mopar one and save yourself some headaches IMO.
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Old 11-07-2013, 10:56 AM   #14
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Lot's of good info already. I prefer the 5W-30 weight oil over the 5W-20 though, especially with the higher RPMs these motors like. The oil classification is much more of a determining factor that the weight. Chrystler recommends an oil classification of ISLAC-GF4 or MS6395 in the Jeep JK. As long as you meet or exceed this classification then it is compatible as this is what the engineers designed the engine to run with, the manufacturer simply used the lighter 5W-20 to hit a target CARB fuel rating.

The Seafoam will do a fair job of de-carbonizing the engine. However, it is better to change driving habits to eliminate or at least reduce the conditions in which promote the carbon to build up around the rings and valves in the first place. Carbon will form when the cylinders become overheated and heat soak the engine components. When the oil hits these components the additive package as well as many of the lesser chemicals will almost flash off from the heat, the carbon however, will adhere and start collecting on valves and pistons. This heat is exagerated by low RPM/lugging of the engine. By keeping the RPM's higher in the RPM range (within reason) there is more power produced which will easier move the vehicle along and create less heat. Another side benefit is that with the little higher RPM the cylinder pressure is greater which will also allow less oil to pass the rings as blowby and contribute to carbon buildup.

As far as PCV valves, they are a check valve that controls the crankcase pressure and allows this blowby to be reintroduced into the intake system to be burnt. When the PCV valve starts to get restrictive it makes it harder for these gasses to be removed from the crankcase. This in turn will find the "week" point in the system. Either a gasket/seal will fail/leak due to the higher than normal crankcase pressure or the vapors carrying oil will travel past the rings and the process keeps repeating compounding the issue. Back in the old days we were told that if you shake the PCV valve and you hear the valve rattle inside, it is good. Not so, they can still either not seal which is uncommon, or start to become restricted and not pass the proper amount of vapors which is much more common. They are cheap and easy to replace so I suggest they get changed on a more routine basis.

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Old 11-07-2013, 12:21 PM   #15
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Consider a trade in.
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Old 11-07-2013, 01:35 PM   #16
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Another thought, I have read in several FSM's as well as an oil seminar that I went to several years ago that a degree of oil consumption should be anticipated in all engines. I had often pondered this earlier in my career but after reading/hearing that and in my 25+ years of experience now, I have come to accept this premise. Some just go through more than others but some should be anticipated and accepted.

The industry standard seems to be one quart of oil per thousand miles on gasoline engines. Ford states this in their service manuals as well as GM but I cannot remember if GM states theirs in the FSM or the Owners/Operators manual.

Chrystler actually dials it down even more specific. They state for a gasoline engine with less than 50k miles it should be the industry standard @ 1 qt./1k miles. For a gasoline engine with over 50k miles it is 1 quart per every 750 miles.

All that said, it seems the OP is right at the threshold of 1 qt./1k miles. If oil consumption increases then more investigative measures should be taken to locate the issue. However, I think the above posters have given some great suggestions to try to de-carbonize the engine and replace the PCV valve for starters.

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Old 11-07-2013, 09:10 PM   #17
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Wow, lots of info. I can handle the pcv valve. Thanks for the help!!!!!
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Old 11-07-2013, 11:47 PM   #18
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Wow, lots of info. I can handle the pcv valve. Thanks for the help!!!!!
I have an 07, it runs thru oil too.....I changed from that awful 5W-20 oil to a 10-30, and that helped lots. Then I started switching oils at change time until I found the oil that seemed to have the least consumption....
I am currently using Castrol Extended Mileage Vehicle oil in the GREEN jug.
This is a Syn/Dyno blend... So far it seems to be working well, and it's due for a change. I have 4K miles on this change and I have only had to add 1 quart total....
There are LOTS of threads here about oil consumption in the 3.8L engines.
Keep your eyes on the Dip Stick, carry a couple quarts with ya and don't run it low or out. Lots of Spun Bearings .
Good luck with yours..."BH"
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Old 11-22-2013, 07:22 PM   #19
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Ok, changed pvc valve. here is what happened. I pulled and pulled on that thing and it finally came out, BUT, a small piece of the plastic that it slides down into broke off on the side. The valve still snapped into place and the hose clamp still fit tight. Will this be an issue or will I need to just keep an eye on it. Only way to completely fix it would be to install a new valve cover and I don't want to do that unless I have to.
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Old 11-22-2013, 08:33 PM   #20
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put some rtv on it to replace the piece of plastic that broke off, otherwise, you may get dirt/water into your engine, not good
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Old 11-22-2013, 08:45 PM   #21
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What does rtv stand for?
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Old 11-22-2013, 09:32 PM   #22
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What does rtv stand for?
Room Temperature Vulcanizing

When someone refers to RTV, they are usually talking about the gasket maker stuff in a tube.
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Old 11-22-2013, 09:43 PM   #23
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I just add a Vulcan quart of oil after 2,000 miles that gets me to my next oil change at around 3,500 miles.
It's a 3.8, it's what they do, don't fight it.
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Old 11-23-2013, 12:17 PM   #24
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[QUOTE=unodog4;6320426]Ok, changed pvc valve. here is what happened. I pulled and pulled on that thing and it finally came out, BUT, a small piece of the plastic that it slides down into broke off on the side. The valve still snapped into place and the hose clamp still fit tight. Will this be an issue or will I need to just keep an eye on it. Only way to completely fix it would be to install a new valve cover and I don't want to do that unless I have to.[/QUOTE

Pulling the Valve Cover is no big deal.....Even if you break the gasket, they are cheap at parts stores anywhere...Well, cheaper than most parts.
Easy to replace the cover gasket.
If that piece of broken plastic is still inside the cover and if it is big enough to block the oil return port (hole in the heads that lets oil drain back to the crankcase ) ...It may cause the oil to drain back slow and or not at all.
I don't know how big this piece of plastic is, but getting it out should not be a big problem.
It may be stuck inside a valve spring or just laying where it fell.
If you look down the hole where the PCV was, can you see it laying there ?
If so, you may be able to remove it with a screw driver with some grease or something sticky on the end...
Good luck and keep checking the Dip Stick !...... "BH"
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Old 11-23-2013, 01:07 PM   #25
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I got lucky when it broke off and it fell on the outside of the hole and not in it.
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Old 11-24-2013, 09:47 AM   #26
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Yea the 3.8 are notorious oil burners. Mine was burning a quart / 600 miles. Changing oil types didn't help. The dealer put in a new block under warranty. Got 30K on it so far so good.

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