People who watch your channel the first time and don’t know your slang probably think you’re slow lol

Great video and good advice, the 4.0 is basically the AMC 199/232/258 that was first introduced in 1964 as the "Typhoon 6" and really didn't change much until the end. I took a 4.0 out of a wrecked 2001 cherokee and it bolted right into a 74 AMC gremlin with no mods other than a adding an electric fuel pump, the old 258 intake and carb even bolted right on the same place.. One of the best engines ever made that was in use for like 50 years. With some simple "old school" maintenance they can go 300K miles.

Bought my 01 XJ in 2013, sold it with over 311,000 miles. I picked up an '00 XJ last February. It's just getting broke in with 170K miles. Love the 4.0.

We own a stock 2002 WJ 4x4 4L. Awesome vehicle bought before Covid for 4k, one owner. Hands down best vehicle for the money we ever owned.

I daily an 01 TJ with a 4.0 and I love it. I've been un-f**king the prior owner's "updates" for a few years now plus learning how to weld! Good to see you again, Doug!

You don't have to unplug the power rail from the wiring harness to change the plugs. Just move it aside; there's room. Don't argue - there is. You can clean the 4.0, but put a plastic bag over the throttle body and don't use engine "cleaner" around it or rinse in the area with high pressure water- be extra mindful of the TPS. Draining your oil with the filler cap on will not lock the cap on or keep the oil from draining fully. The cap being off may or may not affect draining time, but negligibly, if at all. Do clean the corrosion from your battery. It creates higher impedance between the battery and the starting/charging components, which causes higher load at startup along with less efficient charging, which together, degrade your battery capacity and overall battery life faster. I do use the iridium split tip plugs and get great performance from them for typically 60-70k miles. Modern spark plugs DO provide better spark and last longer in ALL engines. The idea behind newer technology is that it does in fact work better than old.

It's always a great day when Doug uploads a video. I never thought about it, but yeah, a Jeep 4.0 is just like my 64 and 68 Harley Davidson motorcycles. Always go with copper, I replace plugs each season and oil with zinc as needed

My daily driver is a '98 TJ wrangler. All original 4.0 is still going strong. Oil, Coolant, and gas are all needed to run forever.

Spark plugs all are copper cores, just the tips are different. Platinums and Iridiums work fine and will last much longer contrary to what was stated. Also a very easy way to get the extra needed ZDDP just use a diesel oil.

I missed the boot on cylinder 1 once... Made a wired sucking/pooping noise... You can definitely tell something is Wrong if you miss one 😅

Don't spend a fortune on an overpriced, overengineered pile of junk that is the overwhelming majority of modern vehicles. Get an older one and restore it. Cheaper in the long run, better build quality and easy to work on yourself.

I miss my 96 Jeep with the 4.0 it was amazing I got her up to 500k and after that the motor went boom and the frame was shot so I had to let her go but I’m determined to find another one like her

Love the content man. Gotta love an old 4.0. I try to drive mine at least once a week (80+ miles round trip).

In the 80's I worked on many AMC 232's and 253's great engines, very reliable if taken care of!

You’d be better off running a diesel oil in it for zinc content. There’s some VOAs out there that show that subtracting the amount motor oil and substituting the STP it actually lowers the over all ppm of zinc that in just a decent motor oil. It’s basically just motor honey

'97 4.0L with 224,534 on the odometer as it sits right now in the driveway. Just replaced the spark plugs, distributor cap/rotor (ACCEL units) and ignition coil. That had nearly 100,000 miles on them... the cap had carbon tracks and build up, rotor was showing carbon wear. The plugs could have been wire brushed, gapped and reused (didn't though).. Dose not use any oil, starts and runs great.

Last week I bought a case of STP because I was checking out Jeep forums, glad to see you made a video to lock in that it was the good thing to do. Forums can be all over the place with opinions on additives.

Actually, the 4.0 straight six has been around since the AMC days. It's been updated along the way to comply EPA whatnot. Great engine, cheers! :-)

I replaced my coil pack with the viper mod. One of my favorite swaps I've done.

Good video but I would have to disagree with a couple of things. I have a 1999 TJ with over 350000 miles (got it new) and I have used Champion Platinum Power Spark Plugs since I can remember. I do agree that the expensive ones are a waste of money but an upgrade above the cheap coppers have worked out for me. Also, I have never put zinc additive in my oil. Engine still runs like a champ, given it's age. Now I have used synthetic oil since it hit around 100000 miles and as I have mentioned, it runs like a champ. The most important thing I can say is change your oil and spark plugs religiously as well as your ignition wires (as per the manufacturer). The 4.0L is a rock solid engine. If you take care of it, it will last a long time.

Love the tip about always removing the oil filler cap before draining. That happened to me a few months ago on my ‘02 Grand Cherokee when the cap disintegrated in my hand while the oil was pouring out the bottom. After some cursing, begging, pleading and praying, the cap threads came out allowing me to refill and limp to the parts store for a new cap.

watched your older videos on the importance of zinc in the 4.0 and running rotella T5 instead of newer oils. stoked to try the change to rotella in my 4.2L 89 YJ. someone with an 88 comanche commented and said making the switch was a game changer not only for engine wear but also sound of the engine

I recently switched over to the Viper Mod coil and wires. I'd been having problems with misfires and pulling the coil rail and putting it back in every time I needed to do some diagnostics wore pretty thin. Best $90 spent.

Thankyou! definitely appreciate and dig this! Just put a new starter in my 04 4.0 HO today after it sat for 3 years….fired straight up, kinda forgot how much my Family and I Love this thing! CHEERS! Zack Daniels ~

Thanks for the zinc tip! I use mine as a daily & it’s great, but the dirty air filter was making me crazy. Good video!

Same thing on my late 90's OBS's. I have a Silverado, k1500 Cheyenne, and a Suburban. The vortec engines are basically a old school small blocks with fuel injection.

I am GLAD I found this channel. Can’t wait for more

Just sharing some knowledge as a person in California with a 95 4.0 liter that's young in terms of mileage at about 180k. Yes that zinc will wear out your CAT faster and that means you might have more trouble with SMOG. What I would suggest though is that at least in my experience a CAT in a 4.0 liter will usually wear out every 4 years anyways. So what I do now is quite simple, every other smog check, since they happen every two years, I go into my SMOG guy and fail the first time like clockwork. The thing is if you buy an aftermarket CAT from an auto parts store like oreilly or autozone they usually have a 5 year warranty. I already have one on my Jeep from the first time I failed SMOG. So I get the CAT cut at my SMOG guys and then I get a ride down to the store I bought the CAT and ask to redeem the warranty, since it is the only reason I am failing SMOG. Brand new CAT for free and most exhaust shops only charge about 100 dollars to cut and weld a new CAT. More than I would like to pay but it gets the job done to pass SMOG. As far as I know its cheaper than going somewhere to get a "legitimate SMOG check" as I have always been told the going rate on that is about 200 dollars. Been doing this warranty swap game for about 6-8 years now. Another note is that if you go in and and find that you are failing SMOG even though last time you got it smogged two years ago you replaced the CAT, try getting a new O2 sensor. This knowledge only applies to older 4.0s that predate OBD2 as far as I know though. As I mentioned mine is a 95 and my exhaust and emissions systems are incredibly simple. 1 O2 sensor and 1 CAT is all it has and it even predates EGR systems. With that simplicity emissions being high has always been the 02 or CAT for me every time. Even in California where standards are high you can keep your 4.0 in good shape and meet emissions standards.

Best thing I ever did on my 4.0 WJ was the dodge viper coil pack conversion it made a little difference driving but made the maintenance 10x easier.

I'm glad you're back! I've missed the Jeep content!

If push comes to shove, and the oil cap won't come out, you can always pull the PCV out of the valve cover and pour the oil in there. The oil cap position isn't located at any specific position that would be decidedly advantageous other than being a bigger hole. All the oil ends up taking the return passages in the head regardless of where it's poured in. There may or may not be a baffle under the PCV, which would slow down the flow, but still an option.

I haven't been watching much KZfaq lately but when I do watch I always enjoy your channel

Never driven one but I did a little wrenching on a Wrangler with a 4.0, incredibly simple. Great info in this vid! Edit: "Daily a 4 liter" I like it. I'm getting back to dailying my 94 Land Cruiser with a 4.5L, that gets AT BEST 10mpg around town.

"Back in the day" I tried a super duper mega coil on my 98 TJ that was guaranteed to increase midrange and mpg. Not the slightest hint of difference vs. Stock.i had a long uphill pull, and it went to the exact same speed up that hill in same gear. That said, I still have that super-duper coil. It is a godsend on point engines. It currently lives on my 1958 Deere.

Thank you for sharing your knowledge and experience. I see the WJ 4.0 as the last chance to own an old school style reliable vehicle especially if you DELETE anything that has to do with a computer.

Dang nice timing, I just bought one of these witches today with 242k miles and 5 different tire pressures. The break pedal whispers curses and theirs a family of roaches I intend to…evict…but I’m in love with this 4.0 i6 and I can actually crawl under it without lifting…I can and will be wrenching. Subbed ya. 👌🏻

The 4.0 was in fact designed to run on 10w40 motor oil, original specs called for as high as 20w50 in warm climates, 10w30 is the absolute lightest weight oil you should ever put in a 4.0. I run 15w40 in mine.

More junkyard content please!

K suspension single coil is what I did to get rid of that crazy multi coil system.

I run Shell Rotella T6 Full synthetic 15/40 in mine. Loaded with ZDDP

Actually those were 258 cubic inch Rambler engines from I think,1965. They had seven main bearings and were as tough as a box of rocks. Not great on emissions or gas mileage but very rugged!

98 XJ, pretty much just got..couple months old. It's "well loved" looking to do some things with it..just not sure what first. Great video and channel

Outstanding vid (‘02 & ‘03 Grand Cherokee Laredo 4x4, 4.0L I6 owner here)…subbed! And fortunately both of my Laredo 4x4’s are in immaculate condition inside and out, with very low mileage.

i have done the viper coil conversion to my 2001 wj and it is amazing i will never go back to a coil rail ever!!!

Just sold my 96 Cherokee with the 4.0 a few months ago. 543,000 miles ran perfect but the body was completely rotted away

❤ my 2000 Grand Cherokee 4x4, nice and clean, runs like a top with 170k miles, gets about 16mpg with about 75% highway driving

Watching this man pull the "coil rail" stunned me. I've been around numerous 4.0 engines and have never seen one of those. All have run off of a distributor.

What do I wanna see? Well for starters, I really miss your car news videos; your history videos were also really interesting. And finally, it's been so long that I don't really remember what projects you had going, but I do know that I want to see that Dakota project go forward!!! :D

I have wondered where you been, bro! Glad to see you're still at it! Great vid! Much love and respect from N Florida. 😎

I have a '06 Wrangler. This guy knows his stuff. Living in the deep south (Mississippi), I use diesel engine oil. It contains the zinc and other good stuff that the 4.0L needs.

it's so true the 4.0 like copper plugs, i got mine it had iridium or something and it just didn't run quite right, swapped in copper and it runs like a champ

I just started doing my own maintenance on my 94 zj 250k+ miles. I wanted to do a transmission flush and replace the govenor solenoid and pressure sensor. Many have told me not to mess with the transmission at all. Any additional knowledge on this would be great. Awesome video 👍

I'd love to see a series about getting this thing back on the road. My '99 WJ 4.0 has been sitting for a few years because the radiator is blown. I'd love to get her back on the road.

"Do Not Clean The Motor!!" I've always heard and lived by "A Dirty Jeep Is A Happy Jeep!" Mine is a stockish '05 LJ with the 4.0 and while not daily it is driven a few times a week.

Glad as hell I found this channel. Sussex County 2004 WJ owner and I love that damn thing like I love my daughters. Bought it last year and did the normal mods but every weekend out there tinkering and changing things. Love the simplicity of it, the 4.0 even though I’m a V8 guy this I6 is a warrior. My kids love it too. It may be one of the best vehicles I ever purchased and I hope that it lasts as it has 142k from original owner and some standard undercarriage rot but nothing that can’t be cleaned up and Fluid Film coated. Appreciate the insights an straight forward stuff

There's nothing like a good bottle of Shell Rotella T4 use to use that stuff in my 93 GMC it loved it

glad to see you back on the tubes and that the old girl is still kicking... still waiting on that dakota to bark to life tho

Helpful tips, but a stock 4.0L does not benefit from zinc additive. Although it has a flat tappet cam, the valve spring pressures are so low, that all a Zinc additive is doing is killing your cat convertors. 4.0L's are known for shedding lots of iron in used oil analysis (mainly from the timing chain) and I had several reports from a few of mine with single digit iron wear numbers on regular modern Pennzoil 10w30 and Valvoline 10w30. A brand new engine that hasn't been broken in, or a 4.6L stroker with an aggressive lift cam is a different story, but the break-in on those usually includes running at a sustained RPM for a period of time with a high zinc oil to break in the cam. Check out the jeepstrokers forum. ;)

Champion cheap is what that engine likes. I put fancy ones in mine and drove cross country and in a few days I went to change the oil and turned it off and then I went to restart it to warn the oil up it wouldn't start. The fancy plugs were clogged up.

I put iridiums in my 2001 wj a year ago and it is running great so far knock on wood.

Those wjs look very nice when you build them up. Wish I had seen it earlier when they were selling super cheap and in really good shape.

You are right on the STP zinc. STP oil filters are well made too.

Dude, you cracked me up with some of what you said. So spot on IMO. Why do so many people overthink everything these day, and some do not think at all and fall for the fake news. My rule as being a Industrial tech over the years is KISS. Thanks for sharing brother. Good stuff. Cheers from Motown.

I daily a '96 xj, and it does great. I've had it for less than 2 years, and it's due for a second oil chage. No major problems(excluding all the cooling parts and leaks and some suspension parts I got fixed when I first bought it) except for camshaft and crankshaft sensors recently, and the alternator. Gas mileage has surprised me quite a bit on the highway. Odometer has low 200k miles, but less than 100k driven miles, because it was towed behind a motorhome. I get anywhere from 12 to 14mpg if I'm lucky, and not driving to crazy around town. Then going on the highway at least 65-70mph loaded or not i've seen 21.5 to almost 24mpg. Not a bad first vehicle, just gotta stay somewhat focused with a solid axle vehicle.

My 95 Jeep XJ that I purchased NEW now has 455,000 miles. Runs perfect, 3,000 mile oil changes uses about 1/4 of a quart. Only internal engine maintenance was a Timing set at about 350,000 just because I thought it was a good idea. 15w40 Mobil Delvac Diesel oil.

I just converted mine to roller lifters and swapped the cam, problem solved. Electric cooling fan conversion, and did a high output distributor. Runs good too, had the head machined to run chevy LS valves, and upgraded the fuel system to also take e85. My 00 TJ Wrangler with the 2.5 is bored and stroked to 3.0L and has a twin scroll turbo and 2 stages of water meth injection. Been tinkering with these motors for years.

Many people with the old corvairs like myself just use shell rotella because we had a oil engineer do some looking and he found out that it is effectively the best stuff to use.

Commented the other day…. My 99XJ with 255,000 was getting 19.5mpg highway this summer. Fresh copper plugs, fresh oil, etc etc and she goes fine… 22psi oil at idle warm and right up over 40psi with a tap of the gas.

enjoyed I'm making an overland 95 XJ It needs some love

I use shell Rotella T6 in my Jeep. Works great. Lots of zinc...

My kind of friend 👊 ..and I'm pushing 308 thousand on my 92 ... best tips on the plugs and oil 🏆 🏆 🏆 ✌️

I just watched your video. Big th!. I'm a 2001 4.0 WJ/WG owner...thanks for keeping my spirits up :). Greatings from Poland

My 4.0 cherokees engine is spotless 😂 I was always told to run Rotella in it 15-40 for the zinc

Doug, I really appreciate your honest sermons pertaining to all things Jeep. It’s been a blessing as I’m buttoning up my engine swap in my 1991 Briarwood. Can you give some likewise insight as to injectors? Mine are the originals, still, after 31 years and 203k miles. Type, brand…what do you use and recommend? My sincere thanks.

Great tips. Hopefully my 2001 4.0 hangs in there.

I really want more of your automotive history videos and the comedy videos ! I watch all your stuff and really dig it, but the comedy and history stuff really shines

My wife’s old 98 zj is now at 223k my dad owns it now but that thing still runs like new

I want to put Bosch platinum +fours in my 4.0. I could feel the difference in the power band, but it causes constant overheating. Switched back to the old school stuff.

Good to see another fresh video bud!

I got the viper mod for my plugs and it is awesome

I own a 2000 WJ 4.0L. Great towing car. Cheers from Australia 🦘

Too true how on some of these old Iron blocks that Sludge and Rust can sometimes be the only thing preventing your motor from leaking oil.

How do you get 25mpg? Probably mine is so heavy but it’s hard for me to get over 17mpg. More often 12 mpg. Thanks this was a helpful video.

always use the recommended plug in the owners manual. pretty simple =)

I just added some Rislone Zinc oil treatment in my 99' XJ Cherokee 4.0 I-6......runs good

I just use Wix filters (mounted via a '87-91 oil filter adapter so I don't have to deal with the T60 torx bit found on later OFAs) and 5w40 T6 Rotella. Motor holds operating temp better, oddly gets better mileage, and runs much smoother than when running 5w30. No leaks either. As for spark plugs, I've found that whether or not the Copper plugs work better is case-by-case. My XJ's old 4.0 definitely prefers copper plugs gapped to .035, and it shows.

Please do a video on the best used Cherokee to buy and what to look out for on one!

Had a 97 TJ with a 4.0 and AX-15 - both lasted over 325k miles original, the frame died first. Was using Rotella T6 with no problems.

definitely love the 4.0, you just can't kill them. Also not sure why you say they get bad milage, I run a tad under 20 MPG, most of that being in the woods with just a little bit in town

Doug good to see you again we missed you!

Beautiful surroundings.

Yuppers, it's plug and oil time as well. Good side is I have the single coil and not the headache one.

I’ve got an 89 Cherokee with the 4.0 litre, and sitting around 175,000 miles so far. I haven’t gotten to drive it much yet, because within a week of picking it up, tranny blew a hole. I did get unlucky too, and am stuck with the Peugeot. Swapping it out has proven problematic because apparently there’s parts missing with the hydraulic throw out bearing (I’m assuming prior owner never bothered to check anything). Mix in some vacuum leaks and needing a new intake, and she definitely shows her age. But damn I cannot wait to get her back on the road. Thanks for the advice about spark plugs and adding zinc in the oil. Hadn’t heard either of those before, so it’s good to keep in mind for the future.

Which do you prefer 4.o or 4.7? I have owned both I preferred 4.0 more robust👍can you do a side by side comparison 🤔 thanks all the way from Scotland

Thanks for the upload Douglas.👍👍👌

I own rusty, dusty, crusty 2002 Jeep GC with the 4.0. Never used oil treatment with the zink or cooper spark plugs. Learn something new every day from your channel. Actually I'm having some kind of issue with the transaction, does not shift in OD. Hope to find some tips on your chanel.

Its about time,lol . Thanks for the video. So far I love my 4.7 , 250k and runs fine.

I've got over 350k on my 98 XJ and 200k+ on my 02 TJ. I run Rotella T5 1030 and I leak / burn almost no oil between changes.NGK copper plugs, LG oil filter. 4-5k between oil changes. Both are lifted , running 33s.

Great video, I've got a 2000 TJ SPORT with 190k on the 4.0L and had to change the starter right before Thanksgiving last year, I chuckled at your starter comment. More importantly, I just picked up my 5th JEEP, a 1996 XJ SPORT with gasp, 388k on the 4.0L.I recently changed the oil and had added the STP oil treatment to it before I saw your video. It runs great but I already was about to change the plugs, wires, cap and rotor, yes a 1996 still has a distributer. I didn't know about the preference of Copper plugs as I'd already bought an Iridium set. I haven't gapped them yet so I'll probably run back up to the parts store and get some cheapo copper ones instead. Great fun video, cheers from Cheyenne, Wyoming, I run my JEEPs at just over 6,000 feet elev., JEEPS RULE!

Cheers from a Land Rover enthusiast and petrolhead!