Pics of oil filter on KJ after first synthetic oil change.

Motorcraft​

400s​

Just wanted people to see how good synthetic loosens sludge.
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WOW nice to know!!!!

Wow. Just a warning I got from a mechanic about switching to synthetic on higher mileage engines. He told me that he has seen a few motors that were destroyed because the synthetic broke up deposits past the filters and it was dragged through the motor. Obviously, you are very aware of changing the filters and maintaining the motor, but I felt like I should mention that to others that could be considering switching to synthetic on a higher mileage motor.

Thats pretty crazy. I cut one of mine open once and it seemed pretty clean besides some red specs. Never figured out why they were in there.

desertkj said:

Wow. Just a warning I got from a mechanic about switching to synthetic on higher mileage engines. He told me that he has seen a few motors that were destroyed because the synthetic broke up deposits past the filters and it was dragged through the motor. Obviously, you are very aware of changing the filters and maintaining the motor, but I felt like I should mention that to others that could be considering switching to synthetic on a higher mileage motor.

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This was after 3K.​

I heard the 3.7s are prone to sludge, which I think is true. The engine oil that I had in it was Q-horsepower, it's doing its job very well. Just so you know, the Jeep was bought used. I do not know if the past owner kept up with maintenance, but the trans & PS fluid where both low when first checked. Original oil was also very watery. The KJ had only 97K when bought (was switched over to synthetic the first day).

The oil filter wasn't nearly as dirty on the 4.0 WJ after I switched to synthetic oil made for diesels (the 4.0 likes diesel oil), even after 6K.
Diesel oil actually has more detergents than regular oil so it should of cleaned the engine even faster. Now I wont lie, I had an oversized FL-1A oil filter on the WJ, it's about 2 1/2 - 3 times larger then the KJ oil filter. The WJ also had its oil changed regularly. The WJ had 140K when switched to synthetic.

^^^ Interesting. With mine, I ran dino up to around the first 10,000 miles or so and then switched to Syn. I have been changing mine between 4,500-5,000 miles.

trail rated.....So it looks like that was run on dino before you bought it probably?? I wonder if you put syn and a new filter in and pull the filter at around 2,000 miles and check it again???

Jeepster....I wonder if that red stuff was in the filter to begin with??

Dave

I have 58K on the 06 Liberty I bought, and switched to synthetic last week. However, I use 10w-30, not 5w-30, the 18.00 Quakerstate deal at Wal*Mart. I have ALWAYS used synthetic in ALL my vehicles, even my Motorcycles, and the one I have now. My V6 Avenger had 150K miles on it, ran 10w30 in that, and 10w40 in the summer, NEVER had any problems. The engine ran as good as the day I bought it, no stammers, vibrations, stutters; nothiong, and that was even with a Delrin front solid mount. I live by synthetic, and will continue to use it. Maybe I am lucky, but it works for me, and I will continue to use it.

If sludge is an issue, when you change to Syn & new filter, drive it for 500 miles, then change filters, and top off.

So, the FL-1A is a LARGER filter, does it fit the 3.7? I did the same with the Avenger, it used a 16, then I found the 8A which is twice as long. Oil pressure was much better too, and more volume.

Powerslave said:

So, the FL-1A is a LARGER filter, does it fit the 3.7?

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No, it will not fit the 3.7.

trail rated said:

No, it will not fit the 3.7.

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Yes, it will. FL-1A = PH8A = Wix 1515 = NAPA 51515 etc. You will find that many folks run the larger filter on their Libbies. BTW, Wix/NAPA Gold are much better than the orange can of death. Purolator is pretty good, too.

A filter that fits a 4.0 will NOT fit the 3.7. Weve got two 4.0's and they use the same filter as the hemi but not the 3.7. The 3.7 and the 4.7 have the same filter since they are the same engine though.

JeepJeepster said:

The 3.7 and the 4.7 have the same filter since they are the same engine...

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No, the FL-1A filter will fit the 4.7 in the WJ. It's actually very popular on the WJ forums.
However, the FL-1A will not fit the KJ 3.7.

Yea, I was wrong about the 3.7 and 4.7 having the same oil filter. Wonder what the difference is? Does the 4.7 just use a bigger filter or is it all different?

trail rated said:

No, the FL-1A filter will fit the 4.7 in the WJ. It's actually very popular on the WJ forums.
However, the FL-1A will not fit the KJ 3.7.

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In the past I put a lot of FL-1A's on a Ford Bronco 11. So if I remember right it is not only longer but bigger in diameter and so the filter gasket probably has too big of a circumference for the KJ. I am just guessing here because it has been a long time since I was using the FL-1A filters.

But you would think since the 3.7 is a 4.7 minus 2 cylinders it would fit, so they must have changed the filter mounting.

Dave

3.7L susceptible to sludge? Since when? Only cases I've heard of 3.7L sludge is with poorly maintained engines, and ANY poorly maintained engine can and likely will have sludge issues.

Either way it goes, I am considering using synthetic for the first time... (well my 2.8L CRD doesn't count since its required...) just to have a longer interval because I'm sick of going to get oil changes every month or so.

trail rated said:

No, the FL-1A filter will fit the 4.7 in the WJ. It's actually very popular on the WJ forums.
However, the FL-1A will not fit the KJ 3.7.

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Yes it will.The 3.7 uses a very popular Ford filter which has the same gasket size(diameter) and threads as the bigger 1qt Ford filter.It will clear the serp belt also,not by much but it does fit.I ran the big Ford filters for some time but it got to be a hassle since you now need 5.5qts instead of 5qts.

Dave said:

In the past I put a lot of FL-1A's on a Ford Bronco 11. So if I remember right it is not only longer but bigger in diameter and so the filter gasket probably has too big of a circumference for the KJ. I am just guessing here because it has been a long time since I was using the FL-1A filters.

But you would think since the 3.7 is a 4.7 minus 2 cylinders it would fit, so they must have changed the filter mounting.

Dave

Click to expand...

The KJ's 3.7 has the exact same filter mount as any 4.7 V-8.

WIX 51516 (standard filter)

Style: Spin-On Lube Filter
Service: Lube
Type: Full Flow
Media: Paper
Height: 4.828
Outer Diameter Top: 2.921
Outer Diameter Bottom: Closed
Thread Size: 3/4-16
By-Pass Valve Setting-PSI: 8-11
Anti-Drain Back Valve: Yes
Beta Ratio: 2/20=14/31
Burst Pressure-PSI: 275
Max Flow Rate: 7-9 GPM
Nominal Micron Rating: 20

Gasket Diameters
Number O.D. I.D. Thk.
Attached 2.734 2.430 0.226


WIX 51515 (oversized filter)

Style: Spin-On Lube Filter
Service: Lube
Type: Full Flow
Media: Paper
Height: 5.178
Outer Diameter: 3.660
Thread Size: 3/4-16
By-Pass Valve Setting-PSI: 8-11
Anti-Drain Back Valve: Yes
Beta Ratio: 2/20=13/23
Burst Pressure-PSI: 290
Max Flow Rate: 7-9 GPM
Nominal Micron Rating: 19

Gasket Diameters
Number O.D. I.D. Thk.
Attached 2.834 2.462 0.200

Ok, I will see if the FL-1A filter will fit on the next oil change.

I just installed a NAPA Gold 1515 this afternoon.

FL-1A filter fits with no problems.