drinnt

Hey everyone, just thought I would beat my dead horse since all the other ones are beat to mush.

My JK has been burning oil for about $15,000 miles now. About a quart every 1,200-1,500 miles. I've read all the stories and reports online. Well, not all...but enough to feel like I keep reading the same stuff over and over. Everything from Mexican assembly to bad gaskets, PCV valves, etc... I figured I would dive into my Jeep and get some answers.

This weekend I took out the plugs and did a full compression test. Other than one plug core being pure white...which was REALLY WEIRD...and all the other scored normally, everything checked out. One of the plugs had a stronger plastically smell than the others. But every cylinder checked out at 187psi and one at 184 which (within 10% of the others) I'm willing to chock up the reading being off from debris down by the fitting. I didn't bother to retest that because others I retested were fine...plus it was well within tolerance.

So, after all that work I know my internal parts, rings, seals, gaskets, valves are mechanically sound...at least in as much as I'm getting proper compression in all cylinders. Where is the oil going? Who knows. I'm going to 5w30 on the next oil change in a few months. I read enough to accept that the difference in viscocities between that and 5w20 to be acceptable. We'll see what happens running it for a couple oil changes. Non-synthetic.

If and as anything develops I will post up my saga as it unfolds so others can learn as I have learned from them.

SoK66

There's a lot of speculation on the root causes of the 3.8L's oil consumption issues, but, assuming no obvious internal issues, the common cures, or at least improvements, seem to be a change to higher viscosity oil, a fresh PCV valve and perhaps investigating leaking intake manifold gaskets. As a former ASE Master Tech my experience says internal engine sealing is pretty simple, starting with cylinder / piston tolerances, proper oil control rings, ring stagger, tension & wear, valve guide to valve stem tolerance and sealing, PCV valve sealing, etc. The list can go on, but those are the basics. The 3.8L has a rep for oil consumption in virtually every application in which it has been used, JK, minivan, etc. What's odd is some suck oil like there's a hole in the pan, others don't use any at all, and some like mine are in between. Mine uses about 1/3 - 1/2 qt. between 3,000 mile oil changes, just enough to be annoying.

I started to notice oil consupmtion at about 15-16k miles, so at the 18k change I switched to 5w-30 oil based upon some forum recommendations. Plus, the manual calls 5w-30 "acceptable". Consumption for the next 25k stayed about the same. I dug into this a bit further at that time and found that it had a leaking PCV valve (upper & lower pressed sections loose). I changed that out and it seemed to stop consumption totally. I recently learned factory remanufactured 3.8L long blocks now come with a 10w-30 oil recommendation, not 5w-20, and that makes some sense. The engine design is nearly 25 years old and was originally spec'd for 10w-30. My local service manager opined that absolutely nothing was done to tighten up tolerances on the 3.8L before Chrysler inexplicably spec'd 5w-20. My suspicion as a former factory guy is someone in engineering discovered it would get a couple tenths better mileage on 5w-20. So, at the last oil change I bumped it up to 10w-30 and the engine seems happy as a clam. That annoying start up clatter is much reduced, as is all that higher RPM valve clatter. Engine seems much quieter over all. With the loads on a heavy JKUR and high operating temps, seems a higher viscosity makes sense.

Tuto

Some people have posted that replacing the PCV valve have stop the oil consumption. So, you may want to look into that.

AR-Fifteen

I have an '08 with 70,000 miles on it and had a complete long block installed and covered under a lifetime power train warranty 10,000 miles ago. I run 10w40 in the new motor, runs like a champ, no consumption, yet. My tech at the dealer, whom I'm friends with, said they switched to 5w30 for fleet mileage.

drinnt

I had not considered a jump up to 10w30. The PCV valve is definitely on the short list. I want to see what she does with 5w30 over the next 6k. If that does nothing I'll do the PCV and stay with 5w30. If that does nothing, then by June I should be ready to make a decision on rocking the 10w30. The engine clatter is very annoying. I've been running 93 octane intermittently just because it does away with the clatter, but runs hotter (in theory). There was evidence on the plugs of it running hot, but JK's do. Perhaps in the end 10w30 will solve the problem. I'll be taking it one step at a time. Thank you all so much!

blue project

My 2010 starting burning like there was not tomorrow and the dealership said it's with "spec". I am running a superchips tune and have a lead foot so that might not help the issue. I changed the pcv valve and stopped running synthetic and that helped a bit. The biggest change was when I starting using factory oil, most of the burning stopped!

duluthjk

My dealership told me Chrysler won't do anything under warranty until it burns one quart every 800 miles. I am at about a quart every 1000 miles.

snytribe

I have a 2010 also. Couple of things that I have noticed. One, change the PCV valve. Two, be careful what oil filters you use. I have noticed a big difference in oil consumption with different filters. I burn more with a fram filter. Will not use one of those again. I have 80K on mine and with the molar filter I burn around a quart every 5k. Good luck

Mr.T

See https://www.jk-forum.com/forums/stoc...esults-257928/
I suspect there's less wear with 5w-40, and if there's any less MPG it's un-measurable in real driving. Currently I'm using Amsoil DEO 5w-40 -- maybe I'll get the oil analyzed again and post it.

Regarding the PCV, suggest only using a Mopar valve with the small oil drain-back hole in the top. To remove the old PCV, stick a large phillips screw driver (or anything round that fits in the hole) and then use Vice-Grips on the outside of the upper part of the PCV and pull.

Mr.T

I'll throw out a few more thoughts on oil consumption. Other than leaks, it's down to piston rings, intake valve guide seals, and the PCV system.

The PCV valve may make no difference, but it's cheap and easy to try. As written earlier, suggest using the Mopar valve. If it's passing too much flow, it tends to suck up more oil mist. If not passing enough flow, the engine will tend to sludge up -- especially with short trips. Sludge and varnish can cause piston rings to stick, causing oil consumption [more on this later].

Bad valve guide seals seem like a long shot to me on a 4 year old engine. I think age, more than miles, affects rubber parts.

Piston rings are a prime suspect even though compression tests good. The compression test only tests the compression rings, the lower oil control ring could be stuck or even missing and compression would still look good. In addition to the oil rings sticking, there are typically drain holes in the bottom of the ring groove behind the oil ring which can plug up with varnish/sludge. It's fairly common to try an engine flush product to free up stuck rings and/or un-plug restricted oil control ring drain holes. I've done this several times over the last 40 years with varying degrees of success. What I've used lately is amsoil's engine flush -- And I've let the engine idle for about twice as long as the instructions say before draining the oil.

As far as oil choice goes, higher viscosity usually reduces consumption. The first number preceding the "w" represents cold weather winter start viscosity, and the second number is the 100 C operating temperature viscosity. The https://www.jk-forum.com/forums/stoc...esults-257928/ thread has the usual opinions about strictly following manufacturer's recommendations, as well of those like myself.