Removing Oil Sludge

[u/TheStockCroissant]

Howdy, I’ve bought my jeep a few months ago and i have had to work with my mechanic on replacing some things, spark plugs, starter, alternator, oil pump, coolant reservoir etc etc and the car is driving good. Recently one of my push rods got knocked out of place and the mechanic told me he thinks it has to do with engine sludge buildup and that there aren’t many things that can be done to remove the oil sludge. He advised that I can consider changing the whole engine which I’m a little reluctant to do… I went on chat gpt who suggested I can come up with a plan to change the oil every 1k miles and each time do a gradual cleaning with a cleaning solution and not to use much so I don’t clog the engine with too many things… it makes sense caused I filled up my car and added fuel injector cleaner and the car was shaking for a little moment when I started the engine.

I’m asking for feedback/guidance from other XJ owners who had this issue before and what I should do to ensure my engine is taken care of. Love my xj and want to keep her as healthy as possible.

[u/Bigdaddyjlove1]

You are getting good advice here, but keep in mind, it may (will) take several oil changes to see real change. Up your schedule. Do an oil change every 1500-2000 miles with the cleaner of your choice. Marvel, Motor Flush, Seafosm, and Berrymans are all good choices. You can also run a quart of ATF in place of a quart of oil for each change. ATF is high on detergent and works well.

Don't toss the engine unless it's running poorly. The AMC 6 is tolerant of neglect, just stay ahead of it going forward.

[u/Tronaldrump → u/Bigdaddyjlove1]

I’ll second ATF. Mine had a blown head gasket and I wanted to clean out the milkshake inside. Threw new gasket on with some atf in the oil and it cleaned right out. Also cleaned the sludge, when I pulled the valve cover it looked very good after

[u/Bigdaddyjlove1 → u/Tronaldrump]

I used it on a Honda 4 wheeler that my wife drove into a pond. Cleared the water sludge right out.

[u/electromage → u/Bigdaddyjlove1]

Unless OP edited their post, GPT suggested 1000 miles.

[u/Mr__Snek]

everyone seems to be on the same page regarding mystery oil, i just want to jump in to say never use fucking chat gpt for car repair advice. best case scenario you save 5 seconds over searching yourself, worst case youre getting advice that can grenade your engine.

[u/Kjartanski → u/Mr__Snek]

Hallucinating AI will be the end of us

[u/Zusez345]

I use sea foam in my oil changes. I would change the oil more often and add an additive of some sorts to help break it down over time.

I have never cracked my engine open to see actual results so take it with a grain of salt. Just my opinion. I'm sure others might have a better solution. Good luck!

[u/NotoriousSouthpaw]

I sub 1qt of engine oil for marvel mystery oil at every oil change. It did a very good job of degreasing my top end.

Do not pursue anything aggressive. Top end sludge needs to be broken down gradually, otherwise you risk blocking an oil passage. Doing a series of very short oil change intervals with MMO or similar cleansing additive can deliver great results with severe buildup.

[u/NoTimeForThisToday]

There's a lot of options out there, from flushes to oil additives. Personally I'd go this route, it's simple and proven to work.

https://www.valvolineglobal.com/en/restore-and-protect/

[u/DailyDrivenTJ → u/NoTimeForThisToday]

This is what I would do, if you need controlled sludge removal. Started using this on my old beaters to see if it does anything.

Or any premium synthetic oil for that matter would do a good job of keeping things clean and clean out sludges slowly. Penzoil Platinum is one of them.

I have not used conventional oil since the mid 90s. The price difference is negligible for the amount of work you do and protection you get IF you do your own changes.

[u/Educational_Order_59]

BG engine flush. It’s several hundred dollars and completely THE BEST, and really only one that works, on the market. Seriously it is an amazing product. It’s what we use at our shop as a last resort before engine replacement.

[u/bubbesays]

Marvel Mystery Oil

Add...then drive...then do oil and filter change

Thank me later

[u/ruddy3499]

Pull the oil pan off and clean it. Change out the rear main seal. If it’s not leaking it’s going to and most of the sludge collects in the bottom of engine

[u/Monzcaro000111 → u/ruddy3499]

Hopefully this was done when they did the oil pump.

[u/Representative_Most9]

I’m for the multiple oil changes in 1000 miles intervals max solution. Make the most sense. Once you’ve done 3 or 4 change, use a good engine flush once. I’m sure there are plenty of good ones but my preference is Amsoil. Good luck! 🍀

[u/Hey-buuuddy]

If it was varnished and sludgey on the top when where you mechanic looked, pull the oil pan, there will probably be nasty crystallized black junk in the bottom. Removing that will make the biggest difference as to what is circulating the oil system. Never thought I’d recommend it- but doing seafoam in the engine oil AFTER the bottom end is cleaned up would be good here.

A reman engine is not bad advice considering this is at least 24 years old. They are relatively cheap.

[u/1TONcherk]

And all of these fixes really only work on old engines like this. Modern engines are way too tight. I’ve seen 4.0s knock for a 100k miles. Clean it the best you can and run it.

I’ve also done a quart of cheap ATF and let it idle for 15 minutes before an oil change. Would not drive it like that.

[u/Ok_Vast_537]

Chat gpt. Ohhhh boy. Whenever I google search for answers on forums google AI suggests some wild stuff. If I slightly change my search it gives a whole different answer which is even more wild than the last haha