I switched to fully Syn. Engine Oil. at 185,504 miles - JeepForum.com
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post #1 of 14 Old 10-21-2019, 11:26 AM Thread Starter
3hounds
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I switched to fully Syn. Engine Oil. at 185,504 miles

My 97 Grand 4.0 now has Pennzoil Platinum Full Synthetic High Mileage in it for the first time & it has 185,504 miles on it. I also used an STP BLACK 10,000 High Mileage filter on it. It's bigger than the original 1 they call for, I've always used the bigger Oil filters since it was new. I also use Restore in this engine, it made a difference in my engine since I STARTED USING IT AT AROUND 150,000 MILES.


I've had it in for about 2 weeks now, difference I've noticed. Engine runs + or - 10 degrees cooler at idle when fully hot. Also it sounds different as it warms up, like you can hear everything rubbing inside the engine. That's the only way I can describe it, no ticks or knocks just sounds different. Turns over slightly faster & it's even getting colder in the mornings in PA.


My rear main seal still leaks but no more or less so far ? No other leaks any where else though. Have not checked if getting better gas mileage but I am now doing so.


Want to change front & rear Diff's. to Synthetic also besides it's time to change the gear oil out. I'm hoping to get better gas mileage out of this PIG. It's pretty much stock except for CAI, BORED TB OUT TO MATCH INTAKE, HI FLOW CAT. & MUFFLER & 235/75/15'S ON IT.


Just wanted to share & I'll post GAS MILEAGE CHANGE IF THEIR IS ANY ?

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post #2 of 14 Old 10-21-2019, 01:21 PM
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IMHO synthetic is far better than dino oil.

And no, it doesn't make leaks happen or get worse.
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post #3 of 14 Old 10-21-2019, 01:54 PM
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Quote:
Originally Posted by MaintMech View Post
IMHO synthetic is far better than dino oil.

And no, it doesn't make leaks happen or get worse.
That myth that synthetic causes leaks on old engines has mostly to do with the oil at the molecular level. Synthetic has much more uniform molecules and they are smaller and fit together much better, which is a part its friction reducing properties and advantages. Because of this though, these molecules can fit into gaps smaller than dino oil and can cause the oil to find its way past old tired seals or worn piston rings far easier than dino. They also tend to clean much better and leave behind fewer carbon deposits, partly due to the higher flash point of the oil, so if there is any carbon buildup filling microscopic cracks or gaps in a seal that are preventing a leak, the synthetic oil will over time expose these weak points and find its way out. Synthetic doesn't ever cause the leaks (it doesn't eat away at old engine components or seal materials), they just expose weak points.

But yes, synthetic is vastly superior in performance compared to conventional mineral based oils.

I've attached some pictures to help illustrate what I'm referring to with the molecular structure if anyone is interested.
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post #4 of 14 Old 10-21-2019, 02:11 PM
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I just picked up my 5.2 ZJ a few weeks ago.

It has 155K on it.

Switched to synthetic last week just like all my other cars.
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post #5 of 14 Old 10-21-2019, 02:12 PM
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I just picked up my 5.2 ZJ a few weeks ago.

It has 155K on it.

Switched to synthetic last week just like all my other cars.
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post #6 of 14 Old 10-22-2019, 09:53 AM Thread Starter
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Thanks for the Illustrations, YES I had a rear main oil leak before adding Synthetic but it has not been any worse. Didn't EARLY SYNTHETIC OILS have an acid in them that would attack seals ? I read that on a OIL MANUFACTURERS WEBSITE before switching over ? Can't remember which one though.
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post #7 of 14 Old 10-23-2019, 05:12 AM
Some_Anchovies
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Quote:
Originally Posted by 3hounds View Post
Thanks for the Illustrations, YES I had a rear main oil leak before adding Synthetic but it has not been any worse. Didn't EARLY SYNTHETIC OILS have an acid in them that would attack seals ? I read that on a OIL MANUFACTURERS WEBSITE before switching over ? Can't remember which one though.
You're talking about esters, a chemical compound derived from an acid, which synthetics in the 1970's were created with, but for the last 40 years or so the seal problem has been completely engineered out and the process of creating synthetics has changed dramatically. The esters were tougher on neoprene seals specifically, but you won't be picking up a bottle of synthetic off the shelf dated 1976 so you won't have to worry.

Here is an article on HowStuffWorks that talks about those esters. This information about the leak myth was posted in May, 2010, almost a decade ago.

Synthetics keep getting better as chemists figure out new bonds to add or modify to its structure.
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post #8 of 14 Old 10-23-2019, 01:38 PM Thread Starter
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Quote:
Originally Posted by Some_Anchovies View Post
You're talking about esters, a chemical compound derived from an acid, which synthetics in the 1970's were created with, but for the last 40 years or so the seal problem has been completely engineered out and the process of creating synthetics has changed dramatically. The esters were tougher on neoprene seals specifically, but you won't be picking up a bottle of synthetic off the shelf dated 1976 so you won't have to worry.

Here is an article on HowStuffWorks that talks about those esters. This information about the leak myth was posted in May, 2010, almost a decade ago.

Synthetics keep getting better as chemists figure out new bonds to add or modify to its structure.


Thanks for the article, VERY INTERESTING WEBSITE FOR SURE. The article I read did not say WHAT YEAR they were talking about ?
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post #9 of 14 Old 10-29-2019, 12:58 AM
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The other common cause of oil leaks after switching to synthetic is that it cleans up sludge left from conventional oil, sludge that was helping seal a leak. The leak was always there, the better oil just made it noticeable. All my vehicles run synthetic everything.
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post #10 of 14 Old 10-29-2019, 10:02 AM
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I have a 4.0L in a 98 XJ and a 95 ZJ which have been running standard Mobil One full synthetic oil.

At around 200,000 miles 98 XJ and 217,000 miles 95 ZJ both 4.0Ls started to use slightly more mobile one full synthetic so I switch to a high mileage mobile one full syn.


I've used Mobil One full synthetics engine oils for many years as well as synthetic transmission and differential oils in the 98 XJ.

The 95 ZJ I've been using Mopar Transmission oil and synthetic 75W-140 in the differentials which 95 ZJ's with a NP249 calls for in the manual (not the 75W-90)

The 98 XJ a transmission mechanic passive flushed the AW4 transmission, installing Mopar ATF+4, the transmission then started to shift hard, so later I passive flushed it again installing AMSOIL ATF which is certified for both ATF+4 and Merc/Dex II/III.


Amsoil ATF is rated for up to 100,000 miles between oil changes. So after installing an external ATF filter I'm letting it go past 25-30 K before a drain and fill.

I've always had good luck with synthetic oils in vehicles. If you install a bypass engine oil filter one can significantly extend motor oil changes as a bypass filters down to 1-2 microns. Quality full Synthetic engine oils tend to mostly break down due to getting dirty and oxidation. So a bypass filter can extend the life of full synthetic motor oils.

However to be on the safe side Amsoil only recommends to follow the oil change frequency of the vehicle manufacture for specific engines and vehicles.

The cast iron 4.0L engine, even though it's rated for 7,500 miles between oil changes (standard duty) I change i approx. every 5K unless sever duty such as towing, off-road, etc. If towing, heavy off-road, etc. I then change every 3K.

High mileage full synthetic motor oil are formulated to be thicker than standard full synthetics. Usuallly high mileage synthetic motor oils the PPM of Zinc is higher.

I find Mobil One high mileage to be formulated for engines with wear, worn aged seals, etc. Cast iron blocks I think may tend to last longer than similar size and designed alum. blocks. Typically a 4.0L achieves over 300,000k. I'm uncertain if true but remember one original Jeep owner stating his 4.0L having over 450,000 miles and still running strong without overhaul, only regular maintenance and oil changes.

Here's a chart that list PPM of zinc which appears to be the same for standard and high mileage Mobil One. I remember reading from years past PPM of Zinc mobile one high mileage being significantly higher that standard full syn.

https://mobiloil.com/~/media/amer/us...pecs-guide.pdf

Amsoil website blog - Do Older Engines Need Oil With ZDDP Additives?

https://blog.amsoil.com/do-older-veh...inc-motor-oil/
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post #11 of 14 Old 10-29-2019, 01:33 PM
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Quote:
Originally Posted by MKCoconuts View Post
The other common cause of oil leaks after switching to synthetic is that it cleans up sludge left from conventional oil, sludge that was helping seal a leak. The leak was always there, the better oil just made it noticeable. All my vehicles run synthetic everything.
I alluded to sludge earlier but it wasn't very clear. I mentioned carbon buildup which is kind of fancier way of saying it. The sludge/carbon buildup will act similar to spackling and fill microscopic cracks or gaps in and around a seal, preventing it from leaking. In the case of bad sludge, it could be more like a giant paste covering large areas and preventing a leak.

Quote:
I remember reading from years past PPM of Zinc mobile one high mileage being significantly higher that standard full syn.
ZDDP is a chemical compound comprised of zinc and phosphorus components. The ZDDP levels on gasoline oils have been capped at less than 800ppm of phosphorus since Oct. 2010 when the ILSAC GF-5 specification was introduced. That's why high mileage and standard oils have the same amounts. It used to not be that way. "The ILSAC level for phosphorus has been reduced to protect the catalytic converter and other emission protection equipment"

This certification was for gasoline engines in passenger vehicles. Some previously Dual rated Diesel engine oils like Rotella T-6 still have ZDDP levels over 1000ppm and are what I like to use when I can afford to and are still officially suitable for 2011 and older vehicle emission systems. Otherwise, I change my oil often enough where I don't believe I need to worry about the additives package wearing out and just use some sort of full synthetic. I currently have 275,550 miles (443,455 KM) on the original engine and I drive it everyday. Just keep up with maintenance and the 4.0 will do fine.

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post #12 of 14 Old 10-29-2019, 09:32 PM
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Originally Posted by muddflow View Post
High mileage full synthetic motor oil are formulated to be thicker than standard full synthetics. Usuallly high mileage synthetic motor oils the PPM of Zinc is higher.]
This is false. They are not formulated to be "thicker". They do, however, contain additives that help swell seals to stop and/or prevent leaks. Also, regardless of the type (synthetic, high mileage, conventional, etc.) they can contain only a certain PPM of ZDDP, up too 600 ppm in any -20 or -30 grade oil. Do some brands contain more than others, sure, but at most they can have only have that. Supposedly, and I don't know if this is still true, but a lot of -40 or higher grade oils were not constrained on the amount they could have with the exception of diesel oils meeting CJ-4
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post #13 of 14 Old 10-30-2019, 09:05 AM
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Quote:
Originally Posted by MKCoconuts View Post
Quote:
Originally Posted by muddflow View Post
High mileage full synthetic motor oil are formulated to be thicker than standard full synthetics. Usuallly high mileage synthetic motor oils the PPM of Zinc is higher.]
This is false. They are not formulated to be "thicker". They do, however, contain additives that help swell seals to stop and/or prevent leaks. Also, regardless of the type (synthetic, high mileage, conventional, etc.) they can contain only a certain PPM of ZDDP, up too 600 ppm in any -20 or -30 grade oil. Do some brands contain more than others, sure, but at most they can have only have that. Supposedly, and I don't know if this is still true, but a lot of -40 or higher grade oils were not constrained on the amount they could have with the exception of diesel oils meeting CJ-4
It's actually up to 800ppm of Phosphorus, not necessarily ZDDP. The total level of Zinc can vary within a ZDDP formulation, but the maximum nominal phosphorus levels cannot exceed 800 for GF-5 rated oils. You can see this on the Mobile 1 product data sheets I've attached. Some newer oils are around 650, but they can definitely exceed 600. This was from their data sheet that came out last October.

The thickness of an oil can be different between two oils within a certain viscosity index. Two different brand 5w30 oils can have slightly different measured thicknesses compared to each other and still pass as 5w30 rated oils. Once they exceed a certain threshold, then the oil becomes a different rating, say a 5w40, but 5w30 does not denote a hard-set thickness of the oil to a "T". In the past, most high-mileage oils were at the thicker end of their respective viscosity index thresholds compared to their standard counterparts. This isn't the case today, as some high mileage formulations can be found to be at the thinner end of the viscosity index than their standard oils. The Viscosity of an oil is rated mostly with Kinematic Viscosity in mind, which only measures how an oil flows through a fixed orifice at different temps. High-Temp/High-Shear or HT/HS is a more accurate measurement of effective thickness when the oils are under a load and at more common operating temperatures than the Kinematic rating, which is only takes the forces of gravity into account. But if we examine different oil data sheets, we'll find the Kinematic Viscosity rating, rated in centi-Stokes (cSt), which is measured in to be different across 5w30 oils.Some of the oil fanatics keep track of the thickest oils within certain viscosity indexes and compare them. By looking at the different Kinematic Viscosities of all the different 5w30 oils, you'll find that at 40c and 100c slightly different thicknesses of oil, with most falling around a cSt rating of [email protected], but the thicker ones being around [email protected]

So a high mileage oil can be slightly thicker than the standard version of the oil, but still be classified under the 5w30 "umbrella". Or it can be thinner. It won't be a huge difference, but the difference in seal conditioners between a standard oil and high mileage isn't huge either. The HM oil will just have slightly more, and depending on the make-up of the seal conditioner, could make the oil slightly thicker.
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post #14 of 14 Old 10-30-2019, 03:00 PM Thread Starter
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HOLY CROW , Ancho you have me reading all kinds of things & I have a better understanding of these oils. Wish I would have switched years ago but I know my engines are darn near spotless inside even just running conventional oil's. Thanks for the lesson on oils, I'll be reading for days.


Oh I don't have a rear main seal leak, it's the oil pan ? I had the Jeep steamed cleaned underneath to track down what leaks I have. Unfortunately found my drivers side cab mount is pretty rusted & the rocker panel right in back of the front wheel BIG HOLE, drivers side. The moulding was hiding it ?
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