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Unread 05-11-2011, 07:01 PM   #61
forewheeler
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I guess I'm missing the point???? OK, so I never did check my oil before I learned I'm consuming oil. So what! Can someone please tell me that how checking my oil would have prevented my Jeep from consuming oil? Oh yeah, I WOULDN'T HAVE! My Jeep would have still started consuming oil. I would have just been adding a quart per 1000 a few miles sooner. Great tech work guys. And no, It's not burning or leaking oil. There are no leaks and no smoke or even burnt oil around my exhaust. It's being consumed and most likely turning into sludge somewhere in my engine.
Can't say that expressing my opinion on this forum has helped in any way other then finding out that most of you somehow believe this is MY fault by not checking my oil sooner.
Oh, and based off the driving I do, I change my oil every 5k though the manual says 6k. Am I in the wrong here as well?

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Unread 05-11-2011, 07:08 PM   #62
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Quote:
Originally Posted by forewheeler View Post
I guess I'm missing the point???? OK, so I never did check my oil before I learned I'm consuming oil. So what! Can someone please tell me that how checking my oil would have prevented my Jeep from consuming oil? Oh yeah, I WOULDN'T HAVE! My Jeep would have still started consuming oil. I would have just been adding a quart per 1000 a few miles sooner. Great tech work guys. And no, It's not burning or leaking oil. There are no leaks and no smoke or even burnt oil around my exhaust. It's being consumed and most likely turning into sludge somewhere in my engine.
Can't say that expressing my opinion on this forum has helped in any way other then finding out that most of you somehow believe this is MY fault by not checking my oil sooner.
Oh, and based off the driving I do, I change my oil every 5k though the manual says 6k. Am I in the wrong here as well?

First off, dont get so butthurt. No one BLAMED you for your Jeep burning oil. All that has been said is exactly what you just repeated. You would have known earlier. It would make sense to check your oil every time you fill up, since you follow part of the manual why not follow the other parts?

Also, if you are buring a quart per 1k, and you are changing oil every 5k... dont you think a bell should have gone off in your head when only about 1-2 quarts came out?
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Unread 05-12-2011, 07:29 AM   #63
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If you check it, you won't get down to one quart and fry the engine, moron.


Jesus.
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Unread 06-26-2011, 08:47 AM   #64
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Oil use vs. Viscosity

I just purchased my second Jeep Wrangler (a 2011 Unlimited Rubicon). The biggest car mistake I ever made was getting rid of my 2005 Rubicon (you can't get the 4.0L straight 6 anymore).

Anyway, I was searching about recommended engine oils and came across this forum. After reading this thread I decided to join and post a reply.

I was suprised that there were no discussions about oil viscosity versus oil usage (and whether or not anyone had experimented with heavier oils to see if it helped their oil usage problem). I personally would have no trust in a 5W/20 engine oil unless I lived close to or north of the Artic Circle. Obvioiusly, this is a bit of an exaggeration, but if you do look at recommended viscosities versus temperature a 5W oil isn't absolutely necessary until somewhere near -20F. Now, I do run 5W/30 in my wife's Excursion in the winter but I switch to 10w/40 (Mobil 1 high mileage) in the summer. I just don't trust a thin oil to provide adequate film strength under heavy loads in the summer. It's probably adequate protection for bearings but it may not be adequate for the piston rings and cylinder. Does anyone remember the good ole days when we ran 20W/50? (I grew up in South Ga, very close to FL). What about the diagrams in the owner's manuals that showed 10W/30 oil good down to about 0F? The OHV engine hasn't really changed. The main reason OEMs recommend 5W/20 is fuel economy, NOT because it's better for engine protection (except in extremely cold climates).

For anyone who wants to learn more about motor oils for your car Noria corporation has a very good article available. Unfortunately it costs $15 but for me it was worth the money. It has more than 70 pages of information regarding motor oils and how to choose what's right for you (economics versus protection). Sometimes it's too technical (unless you are a chemical engineer), but most of it is very readable. Here's a link: http://store.noria.com/How-to-Select...load-P105.aspx
I am by no way affliated with them. I merely work in an industry (power generation) where I consider these kinds of articles professional development literature.

Somthing I learned is that multiviscosity motor oils are really thin oils that are made to act thicker and not thick oils that are made to act "thinner" in the winiter. If the VI's (Viscosity Improvers) shear down (which can happen but is less commen nowadays) you are left with an oil that is too thin to provide the necessary protection. When I bought my wife's 2003 Excursion from Carmax I went to a heavier oil at the first oil change. It made too much noise on start up. It hasn't been until the relatively recent past that general aviation aircraft started using multivisocity oils.

I haven't even seen the new Jeep I purchased as I'm out of the country, but after readinig this thread I've warned my wife to check the oil level every time she puts fuel in it.

Maybe this forum will replace my previous favorite (Turbodiesel Register) where I previously read and posted quite often.
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Unread 07-06-2011, 11:48 AM   #65
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The 5-20 is for tolerances only, NOT for temperature ratings.
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Unread 07-06-2011, 12:12 PM   #66
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5W20 has been the recommended oil for the 5.7 Hemi for almost a decade now. I haven't ever read about oil consumption issues with the Hemi. I blame the 3.8 and/or the workers who assemble it for the issue.

Having said that, 5W20 oil IS basically like water, especially when hot. Is that stuff really protecting your engine on a 104 degree day sitting in traffic with the A/C running? Hmm....
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Unread 07-06-2011, 01:00 PM   #67
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Quote:
Originally Posted by xssnbubblehead View Post
.... multiviscosity motor oils are really thin oils that are made to act thicker.....
That's true for conventional oils, but not synthetics.

Quote:
Originally Posted by WXman View Post
Is that stuff really protecting your engine on a 104 degree day sitting in traffic with the A/C running? Hmm....
The operating temp of these engines is around 200F. I don't believe the heat capacity difference between 20 weight and 30 or 40 weight is so great that it would make a difference if your ambient temp is 60F or 110F.

I suspect there would be a greater difference in heat capacity between fresh/clean oil and dirty/sludged oil of the same weight/brand, etc.

Anyone with an oil temp gauge noticing a difference when they put in fresh oil?

Maybe in racing applications it would matter where the op temp is closer to 300F.
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Unread 07-06-2011, 06:27 PM   #68
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Quote:
Originally Posted by forewheeler View Post
I guess I'm missing the point???? OK, so I never did check my oil before I learned I'm consuming oil. So what! Can someone please tell me that how checking my oil would have prevented my Jeep from consuming oil? Oh yeah, I WOULDN'T HAVE! My Jeep would have still started consuming oil. I would have just been adding a quart per 1000 a few miles sooner. Great tech work guys. And no, It's not burning or leaking oil. There are no leaks and no smoke or even burnt oil around my exhaust. It's being consumed and most likely turning into sludge somewhere in my engine.
Can't say that expressing my opinion on this forum has helped in any way other then finding out that most of you somehow believe this is MY fault by not checking my oil sooner.
Oh, and based off the driving I do, I change my oil every 5k though the manual says 6k. Am I in the wrong here as well?
At full level there is quite a bit of oil splashing up into the bores (there is a tang on the sump side of the rod cap that slings oil upward) This oil sling is cooling and lubricating the bottom of the cyl walls, giving a supply of oil for the oil rings to spread out to lube the compression rings, as well as cooling the bottoms of the pistons. At one qt low (where it says add) the amount of oil doing this cooling is cut to about 60%. Temp goes up at cyl wall, drag increases and rings wear faster, temp of piston increases, as does ring temp. Rings loose tension from running too hot. At TWO qts low - still un-noticed by not taking a small amount of personal responsibility in protecting your investment - all this wear inducing heat is DOUBLED and the consumption INCREASES. The hotter the rings and cyl the more oil goes into the chamber. Once those chrome rings are shot - they STAY shot (unlike pure cast iron which can be reseated by high pressure ergo full throttle runs. Once the hash hone in the cyl is glazed it stays glazed. So bottom line - once the level drops the speed at which consumption occurs accelerates exponentially.

At age 19 my daughter (who is the basis of all blonde jokes ever thunk up) noticed her "brand new used" 95 Taurus would take 1500 miles to go half qt low - but then sped up and only took another 1000 miles to go a full qt low. So she questioned the accuracy of the dipstick.( even though a qt would then put it right back on full)

But then she was only able to notice because she diligently checked her oil - this time. Her first car (72 Camaro) ran til the light came on - then did the responsible thing - drove straight home to ask Dad, 23 miles.

No you did not START the problem - but by allowing it to pull a load (increased combustion temperature) at more than one qt low you most definitely helped push the cart over the ledge and made the consumption increase not just on that oil change but forever on!
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Unread 07-06-2011, 06:57 PM   #69
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Quote:
Originally Posted by jwmbishop View Post
At full level there is quite a bit of oil splashing up into the bores (there is a tang on the sump side of the rod cap that slings oil upward) This oil sling is cooling and lubricating the bottom of the cyl walls, giving a supply of oil for the oil rings to spread out to lube the compression rings, as well as cooling the bottoms of the pistons. At one qt low (where it says add) the amount of oil doing this cooling is cut to about 60%. Temp goes up at cyl wall, drag increases and rings wear faster, temp of piston increases, as does ring temp. Rings loose tension from running too hot. At TWO qts low - still un-noticed by not taking a small amount of personal responsibility in protecting your investment - all this wear inducing heat is DOUBLED and the consumption INCREASES. The hotter the rings and cyl the more oil goes into the chamber. Once those chrome rings are shot - they STAY shot (unlike pure cast iron which can be reseated by high pressure ergo full throttle runs. Once the hash hone in the cyl is glazed it stays glazed. So bottom line - once the level drops the speed at which consumption occurs accelerates exponentially.

At age 19 my daughter (who is the basis of all blonde jokes ever thunk up) noticed her "brand new used" 75 Taurus would take 1500 miles to go half qt low - but then sped up and only took another 1000 miles to go a full qt low. So she questioned the accuracy of the dipstick.( even though a qt would then put it right back on full)

But then she was only able to notice because she diligently checked her oil - this time. Her first car (72 Camaro) ran til the light came on - then did the responsible thing - drove straight home to ask Dad, 23 miles.

No you did not START the problem - but by allowing it to pull a load (increased combustion temperature) at more than one qt low you most definitely helped push the cart over the ledge and made the consumption increase not just on that oil change but forever on!
I don't think there is a splash tang on the bottom end of the JK 3.8L engine.
There is a hole on the major thrust side of the rod's big end to lube that side of the cylinder wall. Any other splash oil is from what squeezes out of the rod bearings.

Picture of the bottom end of the JK 3.8:
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Unread 07-07-2011, 08:40 AM   #70
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Roger that and thanks. I have been out of the machine shop long enough to not have laid hands on a 3.8 so had no reference.

Even with positive spray though the splash cooling and lubricity reduces as oil level goes down (less oil means more aeration and contaminates "per capita"). And with reduction of oil volume, heat accumulation (same heat load spread over less oil) and resultant surface heat increases still holds true! And keep in mind a tang does not dip into the sump - it only directs where the bearing bleedoff slings! From an engineering perspective (which always must balance manufacture time, cost of both part and machine tooling and function) when ever you see positive feeders you must realize that added machining step and cost are there for a reason - usually higher piston and skirt temps, secondly deeper piston undersides (where sling just don't make it to the wrist pins).

The positive does slow the acceleration of splash loss with level drop significantly though as a posi just means more total volume to the bottoms - but can be argued that as that total is now more critical - reductions are now more detrimental! Unless there is a windage and scraper - in which case the positive is the only oil that the piston sees so total oil present remains constant until the pump sucks air.
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Unread 07-07-2011, 08:48 AM   #71
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And keep in mind a tang does not dip into the sump - it only directs where the bearing bleedoff slings!
When you mentioned a tang on the rod for slinging oil, the only thing I could picture is the only type of tang I had ever seen on an engine: one that dips into the sump.

What are the tangs you were referencing? Got a picture or a link?

(The JK 3.8 pistons have very short skirts.)
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Unread 07-07-2011, 10:14 AM   #72
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The 2nd generation Small Block Chevy is a prime example of tanged connecting rod (pic below). If you look at the machined surface at the parting line of the cap and rod you can clearly see the step tang. The tang DOES NOT DIP. In order to dip the oil level would have to be so high that the crank ran thru oil (the tang is halfway up the rod journal) - and doing so would kill the slinging effect as the oil wants to stick to itself (one of the reasons overfilling is bad)! This is obviously not the case as the front of the chevy pan is "dry" that is all the oil there runs back into the sump. But what happens is the oil that flows off the bearing and out the sides (bleedoff) is slung by the tang upward to the piston bottom. Oldsmobile rods have an elongated tang for better direction control. ANd typivally oil level is two inches below the farthest arc of the rotating mass - the helps eliminate parasitc losses (engine working to run thru gobs of excess oil is less power avail at the crank end).

As the skirts on the 3.8 are short - obviously the extra oil being sent up there from a positive squirt is for cooling the bottoms - not so much lubing the wrist pin. This makes sense as with computer controls we are running closer to (and even right at) stoichiometric (14:1 air fuel ratio) vs carbs which we tend to run at less than for a safety margin (sometimes at 12:1 afr). Pistons run hotter in todays engines than in the builds of the past - especially when equipped with knock sensor!

The pic I just added shows another way to direct the bleedoff - straight up it's own rod! this is a straight six where one side can not splash the other.
f20043508.gif   dsc00085.jpg  
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Unread 07-07-2011, 10:30 AM   #73
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Thanks.

I knew the rods don't dip into the oil. The tang I was thinking of was one that hangs down from the bottom of the rod cap, and does dip into the oil. That's why your reference to a tang brought me to an incorrect mental picture.

The forced oil from the hole in the JK 3.8 rod is mainly to lube the major thrust side of the cylinder/piston.

Are the arrows in the picture pointing to the "step tang" you are talking about? If so, I had no idea that's what it was for.



I can see where the slot in your second picture would be good for cooling the piston bottom, and lubing the pin.
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Unread 07-07-2011, 10:38 AM   #74
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The top arrow is the splash tang. The bottom step is balancing it weight wise (and thus not as pronounced). I have seen older Buick and Pontiacs where that thing is as wide as the outer edge of the casting. This is one reason it is so important to make sure you have the right orientation on the rods. If you hang em backwards it slings oil away from the opposing piston bank. The other of course being the chamfer - if backwards the chamfers are together and oil is bled off between the rods instead of at the crank side, lowering the pressure at the bearing and over heating the crank at the journal radius.
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Unread 07-07-2011, 01:00 PM   #75
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While it's true that synthetics can obtain a mulitviscosity rating without VII's, some do have it. I can't imagine how Mobile 1 5w/40 turbo truck diesel oil obtains that rating without VII's. A 10w/30 synthetic probably doesn't need it.

The article I referenced talks about how the oil companies actually obtain the energy conserving rating. It basically involves using VII's that "shear down" to reduce friction, which means they will shear down in the 5 micron or so clearance between the rings and cylinder walls.

Obviously, some engines run these lighter weight oils without having excessive oil consumption problems, so obviously not all engines are created equal in this respect. As a note, one of my brothers flies his private plane extensively for his work (probably 10 hours a week). He tells me that he doesn't burn any oil up until it has 25 hours on it, then it starts using oil. He spoke with his A&P mechanic who stated that obviously something in the oil changes (possibly thinning down). He now changes his oil at the 25 hour point. Considering the cost of reman engines on those things it's worth the extra cost & effort. He also "disects" his oil filter every time looking for metal. Supposedly you can keep a close eye on when a reman is needed as they will start showing metal in the filter.

If you're truely worried that sludge is building up in your engine (which I understand is mostly related to condensation of water in the oil and not removing it by heating the oil up; i.e. short trips in cold weather) I'd recommend shortening your oil change intervals. Do a web search for Sludgemobiles and you'll see the engines that people are complaining about. I recall seeing Toyota mentioned a lot and older Durangoes, but I don't remember seeing anything that uses the same engine as the Jeep.

I remember reading an article in Popular Mechanics about 25 years ago (when lighter weight oils first became recommended by OEMs). It stated that the OEM had to recommend the same weight oil as used in the MPG test, thus they almost all now recommend thinner oils. Maybe it really is due to manufacturing tolerences, but which happen first? Maybe it was the use of thinner oil that caused bearing tolerances to get tighter and not the other way around.

Be very careful about overheating your engine if you use the 5w/20 stuff. The article I referenced above states that every 20F increase in oil temperature causes it to act one grade thinner (i.e. a 30w oil would act like a 20w oil when temperature changes from 200F to 220F).
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