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Flushing This Sludged Engine With Diesel... Did It Go As Planned?

Wrenching With Kenny

461,195 views

You asked for it — so we're trying it!
Sludge-Zilla is back, and before pulling the engine I decided to try something many of you suggested: drain the old oil, fill the engine with diesel fuel, run it, and see just how much of that nasty sludge it could clean out.
At least, that was the plan...
After running the engine with diesel, I discovered another major problem that pretty much killed the experiment. But we weren't done yet.
I pulled the engine, checked the spark plugs, cut open the old oil filter, and what we found inside gives us a pretty good idea of just how bad this engine really is.
The engine is still going to be completely torn down in an upcoming video so we can see exactly what happened inside Sludge-Zilla.

⏱ Chapters
0:00 Sludge-Zilla Is Back
0:41 Draining the Nasty Old Oil
2:51 Removing the Old Oil Filter
3:57 Filling the Engine With Diesel
5:11 The Diesel Flush Experiment
6:21 Does This Engine Have Oil Pressure?
8:50 The Diesel Flush Is a Bust
10:13 What 250K+ Equivalent Miles Did to the Spark Plugs
10:50 Engine Out & Cutting Open the Oil Filter
11:49 Wrap-Up

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#EngineSludge #DieselFlush #WrenchingWithKenny

20 Comments

@oneeyedjack4727 1 month ago

A friend of mine bought a Kia a few years back. Erratic oil pressure. Sludged up beyond reason. Nothing to lose so we took the valve cover and oil pan off, took it to a car wash and pressure washed the engine through and through top and bottom. Cleaned the pick up screen and blew as much water out as possible with air. Reassembled with new oil and filter. Hard to believe but it ran! 2nd oil change and he drove it for a year and then the trans went out.

@darrenw2803 1 month ago (edited)

Ive seen people do the diesel trick...but mixed half diesel to half oil when doing a treatment like that

@nasimwehbe8410 1 month ago

It's supposed to be a 50/50 mix of oil and diesel. The engine is supposed to be at idle, not 2000 rpm. I've done it on an old 96 Toyota Celica. Worked like a charm.

@harveysmith100 1 month ago

That engine didn't have 1k left in it. Badly treated.
The worst thing car manufacturers did was remove the oil pressure gauge. It can tell you so much.

@TEENYcharma 1 month ago

“New cars don’t last anymore”

No. New drivers aren’t competent anymore

@ProductCode74 1 month ago

Change your oil folks

@masmainster 1 month ago

Probably half diesel and half some cheap motor oil might have given you some oil pressure.

@crazycajun1572 1 month ago

Old school. Correct process is 1 to 3 ratio and to do it in a step process typically run for 30 min and repeat typically takes 4 times and you should have taken a blow gun to the oil pump pickup because you already knew it was blocked.

@sumtime-c1h 1 month ago

Ive heard of old timers filling a car up to the fill port with diesel and letting it set a day or 2.

@VorpalForceField 1 month ago (edited)

I have heard of plugging the hose ports and filling the engine entirely all the way to the top of the oil fill port and soaking for 24 hours. That was to dissolve and loosen the sludge, but not to run it. Then refilling with cheap fresh oil as a flush run for a number of miles then a fresh change. Likely best to use several oil filters for they will clog with all the sludge.

@10100rsn 1 month ago

6:25 "...may not have any oil pressure..."
That's diesel pressure now.🤓

@stephenamatosr9089 1 month ago

I used trans fluid and a bottle of stp back in the day. Drove it 100 miles. Did lof again twice. Rings seated and ran better but sludge cloged the pickup. Droped pan scraped out. Ran 50/50 40wt/ trans fluid and saved it. But took time. Drove 60,000 miles after. Crazy

@theredscourge 1 month ago (edited)

I've seen videos of people do 3/4 diesel 1/4 ATF and run it for 60 mins and it only put a dent in it. Sludge isn't as important to remove as piston ring gunk, so a cylinder treatment like Berryman B12 Chemtool followed by just doing earlier oil changes is usually far more productive. If that doesn't work, just live with it, it means you either need new piston rings or a new short block.

@21Piloteer 1 month ago (edited)

My 21 Honda Pilot and my wife's 23 Honda Passport get oil changes every 6 months. Following a "severe duty" type schedule due to our mostly stop & go driving. As a matter of fact her Passport is about to hit 30K. It will be getting an oil change, transfer case fluid service, transmission fluid service, and rear diff fluid service.

@brianAndrews-i3q 1 month ago

I bought an 1995 e36 BMW. It ran good but it had an intermittent lifter tick. I pulled the valve cover and the head looked as if someone had dumped potting soil into it. The sludge was plugging the hydraulic lifters, then getting forced out, then plugging another lifter … rinse and repeat. I did the diesel flush and I switched to synthetic oil. Three thousand miles later and the ticking is long gone. I pulled the valve cover and the head is as clean as any well maintained 10 year old car can look. I wouldn’t do it if an engine doesn’t need it … but, if you have an extremely sledged up engine, I am a believer.

@suprakillavr4 1 month ago

There's only one thing for sludge, and that is BG Dynamic Engine Cleaner. It was the only factory approved way to desludge VW 1.8Ts. You have to be very careful using it as it's easy to spin rod bearings and such if you let the sludge block oil passages. A safer way if you don't want to use a mechanical oil pressure gauge and swap oil filters 20 times a day is to just use a bit of cleaner or heavy detergent oil over a long period of time.

@dpmesse 1 month ago

Ive seen the advice to fill the engine to the TOP with diesel, let it sit as long as you can, then drain and run frequent oil changes in the theory the goop will be loosened and start coming loose.

@greggc8088 1 month ago (edited)

Scraping it out is best due to the screen getting blocked up with goo but not here because that engine is toast. I bought a 55K 99 4Runner when it was 3 years old and someone had let it get sludged up really bad. Ran cleaner through it for 10 minutes while watching it and the oil light came on at the 10 minute mark. Turned it off and removed the valve covers and oil pan, which was my first intent as cleaner was just to loosen stuff up, and scraped it all clean. I put about 100K on it after that and sold it.

@2003evodave 1 month ago

I’ve done this diesel flush only running the engine until it warmed up, approximately four to five minutes, drained it changed the filter and oil. Was amazed at the junk that came out. Followed up with additional oil and filter changes until things cleaned up. Ran that truck for ten years and sold it still running great. Big difference is it still had oil pressure to begin with.