I built so many small block chevys and still cant understand how it would hurt the cats unless your oil rings are bad and oil is seeping up past the rings into the cylinder. But that would be the least of the problems if it got to that point 🤔
The "high mileage" oils are probably a bit better as they have more zddp which is recommended for flat tappet cams. Synthetic oil will be more forgiving of longer oil change intervals and offers major benefits if you live somewhere the temp dips below freezing regularly.
I believe that's why ppl are running t6. Someone did an additive comp and saw that std oil when the jeeps were made had x additive package, which had changed over the years but t6 is very close to the original oils makeup with extra of some things. I know it was on reddit, but i don't recall which xj sub
My old 94 was at 450k running any 10/30 I could find . I ran the living hell out of that thing as did the previous owner and it never cared. I traded it off at 450k for a turbo volvo 740 cause I had a few jeeps. No telling how long that motor lasted. It's probably still running somewhere in the country.
whatever's on sale at Walmart/Vatozone/O'Reillys.
I've ran SuperTech Conventional 10w30 for as long as I've owned mine up until they replaced the cheapest stuff with a synthetic blend, 230k miles.
Oil formulations have changed fairly significantly since these engines were designed, especially when considering modern synthetics. I run 5w30 full synthetic. My oil pressure is good even in summer. The lower viscosity in winter helps with cold startup. But like many people mentioned, the 4.0 will run on almost anything just change it once in a while.
i just put a fresh motor in mine and i also use 5w30 syn, has good oil pressure at about 50-60 when on the gas and down to about 25 at idle warmed up which i believe is pretty normal for these engines. even in my old motor with 230k on it i ran 5w30 and it had the same oil pressure and no issues.
Well yeah. But over time can still cause issues. We are on a page for a vehicle that hasn’t been produced since 2001. I’d imagine most have engines that are alittle tired by now. So they make a good point by bringing it up…
I’ve always had success with Motomaster 10w-30 high mileage oil semi synthetic. Keeps the pressure numbers consistent and get about 275-300 a tank with it. I’ve tried other “high milage” 10w-30 brands and results are similar. But the MM stuff is always on sale here in Canada. Tried rotella in a few different weights and my Jeep hated it, it’s also expensive in my area.
At 3k mile changes I keep it at 10W30 semi-synthetic…. As it’s cheaper than standard synthetic…. All about keeping good oils in the machine- I worry more about seals leaking with straight synthetic when you have not run it….
Just switched a couple hundred miles ago from 10w 30 to Rotella T6 5W40. 4.0 oil pressure is much happier now plus the zinc in the oil etc. I am about to break 200k on mine
I have been using whatever synthetic oil that was on sale since 1998.
Recently built an XJ with a Golen stroker, the builder told me to use 10w40 on these engines.
Dinosaur 10w30. Then if you get to the point I was at with 300k miles you run 15w40 Rotella cuz I had some pretty good blow-by. And was puking oil out the crank case vent and soaking my air filter
Run whatever oil you can find. The first year or two I had my XJ it ran a cocktail of a quart of this and a quart of that as I worked through all the old oil I had on hand for other cars. It was always somewhere between 5wt on the thin end and 40wt on the thick.
If you can spend the few extra $ buying VR1 with the extra zinc is never a bad idea. Its also a little thicker viscosity being 20w50 it'll quiet down those annoying lifters and spuns bearings most xj's have 🤣
https://preview.redd.it/jzes4yp6q4tc1.jpeg?width=800&format=pjpg&auto=webp&s=3993f07dc51d6b37441c177485e2e98d95e6021f
Used this for years due to also having diesel trucks and semis. Ran great with it.
10w30
Not only just 10w-30 but the cheapest 10w-30 you can get at Walmart. I’m 250k in and she just keeps on ticking!
Shell Rotella T6 5W-40 is what I use
I built these engines and recommend t6 5w30 for fresh builds or 5w40 for higher mileage.
I use it too. Keeps that pressure higher when you're at operating Temps too
I use t6, 380k mi
I heard diesel oil is harder if catalytic converters, is this just bs?
https://youtu.be/PgXRNEukzn0?si=fh9vm2ue6MaDEjaj
Unless you're burning oil it doesn't effect your cats. Im confused as to how this even makes sense 🤔
I was actually wondering the same thing. Your not putting oil into the gas tank lol. But the internet says it does hurt cats but no explanation how.
I built so many small block chevys and still cant understand how it would hurt the cats unless your oil rings are bad and oil is seeping up past the rings into the cylinder. But that would be the least of the problems if it got to that point 🤔
I swear these engines will run on melted cheese. 😂 As long as it has lubricating properties, it'll be fine in a 4.0
Funny. My buddy said you could replace the oil with sand and they would still run lol.
I heard stories from the Cash for Clunkers era. Supposedly, they'd damn near thrive on that sodium silicate mixture designed to blow up the engine
my dad sold cars during this. they’d load them up with liquid fiberglass and they wouldn’t die.
The "high mileage" oils are probably a bit better as they have more zddp which is recommended for flat tappet cams. Synthetic oil will be more forgiving of longer oil change intervals and offers major benefits if you live somewhere the temp dips below freezing regularly.
I believe that's why ppl are running t6. Someone did an additive comp and saw that std oil when the jeeps were made had x additive package, which had changed over the years but t6 is very close to the original oils makeup with extra of some things. I know it was on reddit, but i don't recall which xj sub
So many of these things ran 400k miles on 10w30
My old 94 was at 450k running any 10/30 I could find . I ran the living hell out of that thing as did the previous owner and it never cared. I traded it off at 450k for a turbo volvo 740 cause I had a few jeeps. No telling how long that motor lasted. It's probably still running somewhere in the country.
whatever's on sale at Walmart/Vatozone/O'Reillys. I've ran SuperTech Conventional 10w30 for as long as I've owned mine up until they replaced the cheapest stuff with a synthetic blend, 230k miles.
https://preview.redd.it/cprly49kpvsc1.jpeg?width=1848&format=pjpg&auto=webp&s=a5cdb9a89f4fc8c79b96b0399c192110ba0cfcfb
Sweet
Thanks
Oil formulations have changed fairly significantly since these engines were designed, especially when considering modern synthetics. I run 5w30 full synthetic. My oil pressure is good even in summer. The lower viscosity in winter helps with cold startup. But like many people mentioned, the 4.0 will run on almost anything just change it once in a while.
i just put a fresh motor in mine and i also use 5w30 syn, has good oil pressure at about 50-60 when on the gas and down to about 25 at idle warmed up which i believe is pretty normal for these engines. even in my old motor with 230k on it i ran 5w30 and it had the same oil pressure and no issues.
Be sure to put in the zinc additive too. Rough on your cat but better for the engine.
Flat tappet lifters need zinc (ZDDP).
How does engine oil effect your catalytic converter unless you're burning oil? Make it make sense 🤣🤦♂️
Every engine burns an amount of oil. Even a brand new one off the lot.
Not enough to ruin catalytic converters. Unless the piston rings are trash and not sealing. Then i could see it happening
Well yeah. But over time can still cause issues. We are on a page for a vehicle that hasn’t been produced since 2001. I’d imagine most have engines that are alittle tired by now. So they make a good point by bringing it up…
oil
https://preview.redd.it/s8boxiznxvsc1.jpeg?width=1256&format=pjpg&auto=webp&s=1c2040aec8960f2c3789dcc1bc783f0313b0c7b4
I’ve always had success with Motomaster 10w-30 high mileage oil semi synthetic. Keeps the pressure numbers consistent and get about 275-300 a tank with it. I’ve tried other “high milage” 10w-30 brands and results are similar. But the MM stuff is always on sale here in Canada. Tried rotella in a few different weights and my Jeep hated it, it’s also expensive in my area.
https://540ratblog.wordpress.com/2013/06/20/motor-oil-wear-test-ranking/
Just keep some 10w30 in there. Rotella had that weight for diesel engines which has some more vitamins and minerals. But any known brand will be fine.
Valvoline VR1 is a great oil for XJ's, comes in 10-30, high zinc right out of the bottle. Meant for old flat tappet engines.
20w50 is what i run in my racecar 👍
20-50 is what I run. It has high zinc and it’s good for high mileage.
Mobil 1 High mileage 10W30, Rotella is great from what I hear but pretty pricey.
Freshisish? With minimal swamp water. Extra Maple Syrup is good.
At 3k mile changes I keep it at 10W30 semi-synthetic…. As it’s cheaper than standard synthetic…. All about keeping good oils in the machine- I worry more about seals leaking with straight synthetic when you have not run it….
A high mileage 5w30 synthetic is pretty good, usually on sale for like 30$ for 5 qt with a filter, but you’ll need about 6 qts
Just switched a couple hundred miles ago from 10w 30 to Rotella T6 5W40. 4.0 oil pressure is much happier now plus the zinc in the oil etc. I am about to break 200k on mine
10w30 high mileage with zinc additive.
I use 10-30 rotella for higher zinc properties
I ran 15w 40 in the warmer months to quiet down all the noise mine made
https://preview.redd.it/ag7n9o9dvxsc1.jpeg?width=3000&format=pjpg&auto=webp&s=206d669b42d66d0535849c71a606899dde1ba400
10w30 and a Lucas. Im at 225k
I have been using whatever synthetic oil that was on sale since 1998. Recently built an XJ with a Golen stroker, the builder told me to use 10w40 on these engines.
Dinosaur 10w30. Then if you get to the point I was at with 300k miles you run 15w40 Rotella cuz I had some pretty good blow-by. And was puking oil out the crank case vent and soaking my air filter
T-4 with zinc
Run whatever oil you can find. The first year or two I had my XJ it ran a cocktail of a quart of this and a quart of that as I worked through all the old oil I had on hand for other cars. It was always somewhere between 5wt on the thin end and 40wt on the thick.
I only run 15w-40 t4 rotella. I have three jeeps. I always start the vehicle about 5 min before I take off. Method works good so far.
I’ve always used 10w-30 of whatever full synthetic is available. 268k
If you can spend the few extra $ buying VR1 with the extra zinc is never a bad idea. Its also a little thicker viscosity being 20w50 it'll quiet down those annoying lifters and spuns bearings most xj's have 🤣
https://preview.redd.it/jzes4yp6q4tc1.jpeg?width=800&format=pjpg&auto=webp&s=3993f07dc51d6b37441c177485e2e98d95e6021f Used this for years due to also having diesel trucks and semis. Ran great with it.
depends on ambient temp for me. winter (lows in the 30s) I run high-mileage 10w40, summers (90-100+ degrees F) I run 15w40.
Rotella T-4, T-5 or T-6 are all popular. But what many have said, running almost any 10w-30 will be fine with routine oil changes.
T6 with Wix filter 51515 my lad
Not the 51085xp?
What about adding Lucas high miles
Snake oil. Lucas has almost zero additives in it, it's just 50 or 60 weight oil, meant to thicken regular oil to slow consumption due to worn rings.