I have a 2004 Jeep Wrangler with the 4.0. I bought it last year with 73K miles on it. My first oil change I went with mobile full synthetic 10W-30 because that is the brand oil I have used for years now in my vehicles. It might be in my head but the slight leak at me rear main seal seemed to drip more after the oil change, so next change I switched to the mobile 5000 conventional oil with a mopar filter and the rear barely seems to drip. I have been doing an old school 3K OCI. How does this sound? Advice on oils or OCI???
Jeep Wrangler 4.0 with Mobile Conventional?
- Thread starter The Shape
- Start date
- Status
If you're doing 3k oil changes I would skip any synthetics. All it is doing is draining your wallet. I have heard a lot from Jeep owners that the 4.0s loved Shell Rotella HDEO. Considering where you live you could get away with 15w-40 or 10w-40. I would recommend that and go for 5-7k with a quality filter. If you don't wasn't to use HDEO I would use Supertech conventional 10w-40 and if you want to stick with 3k I would with supertech filters and if you want to go 5k or higher I would recommend using something like a wix or fram tough guards. Even Motorcraft would be good for your application
I put nearly 200,000 miles on a Cherokee with a 4.0L I-6 and AW-4 auto using a wix 51515 and Mobil Clean 5000 10W-30 (now Mobil Super 5000?). Did an annual drain and fill on the ATF in both the AW-4 and NP231. OCI was 5,000 miles.
Sold it a few years ago and it was still running like a top. No clue where it is today.
Edit: I also had a very small leak from the rear main. Never fixed it because it wasn't enough to even see a drop on the dipstick between changes. But, from what I read the rear main on the 4.0 is pretty easy. Only the pan has to be dropped, transmission does not have to be pulled. Don't know from first hand experience though. So if you wanted to run synthetic you could just fix the rear main seal.
Sold it a few years ago and it was still running like a top. No clue where it is today.
Edit: I also had a very small leak from the rear main. Never fixed it because it wasn't enough to even see a drop on the dipstick between changes. But, from what I read the rear main on the 4.0 is pretty easy. Only the pan has to be dropped, transmission does not have to be pulled. Don't know from first hand experience though. So if you wanted to run synthetic you could just fix the rear main seal.
Last edited:
Originally Posted By: WMW0505
I put nearly 200,000 miles on a Cherokee with a 4.0L I-6 and AW-4 auto using a wix 51515 and Mobil Clean 5000 10W-30 (now Mobil Super 5000?). Did an annual drain and fill on the ATF in both the AW-4 and NP231. OCI was 5,000 miles.
Sold it a few years ago and it was still running like a top. No clue where it is today.
Edit: I also had a very small leak from the rear main. Never fixed it because it wasn't enough to even see a drop on the dipstick between changes. But, from what I read the rear main on the 4.0 is pretty easy. Only the pan has to be dropped, transmission does not have to be pulled. Don't know from first hand experience though. So if you wanted to run synthetic you could just fix the rear main seal.
Depends on the model for the rear main seal. Changing the seal itself is relatively easy, but getting the oil pan off is the hard part. On a TJ Wrangler , the exhaust flows forward and under the oil pan , so part of the exhaust has to come off. On a Cherokee all you really have to do is maneuver it around the front axle.
The newer 4.0Ls don't really have the rear main seal problems that the older ones had. The way the engines are oriented in the vehicle, any leaks will run towards the back of the enginee and down the back of the block. Unless it's coming out of the starter or the bellhousing, I'd lean more towards an oil pan gasket, valve cover or oil filter housing adapter. A lot of people get diagnosed and pay for a rear main seal replacement, and their jeep does stop leaking ,but it was the oil pan gasket that was the problem the whole time.
But for a 3000 mile oil change interval I wouldn't even bother with a synthetic or blend. I'd go with good ol' conventional 10w-30.
I put nearly 200,000 miles on a Cherokee with a 4.0L I-6 and AW-4 auto using a wix 51515 and Mobil Clean 5000 10W-30 (now Mobil Super 5000?). Did an annual drain and fill on the ATF in both the AW-4 and NP231. OCI was 5,000 miles.
Sold it a few years ago and it was still running like a top. No clue where it is today.
Edit: I also had a very small leak from the rear main. Never fixed it because it wasn't enough to even see a drop on the dipstick between changes. But, from what I read the rear main on the 4.0 is pretty easy. Only the pan has to be dropped, transmission does not have to be pulled. Don't know from first hand experience though. So if you wanted to run synthetic you could just fix the rear main seal.
Depends on the model for the rear main seal. Changing the seal itself is relatively easy, but getting the oil pan off is the hard part. On a TJ Wrangler , the exhaust flows forward and under the oil pan , so part of the exhaust has to come off. On a Cherokee all you really have to do is maneuver it around the front axle.
The newer 4.0Ls don't really have the rear main seal problems that the older ones had. The way the engines are oriented in the vehicle, any leaks will run towards the back of the enginee and down the back of the block. Unless it's coming out of the starter or the bellhousing, I'd lean more towards an oil pan gasket, valve cover or oil filter housing adapter. A lot of people get diagnosed and pay for a rear main seal replacement, and their jeep does stop leaking ,but it was the oil pan gasket that was the problem the whole time.
But for a 3000 mile oil change interval I wouldn't even bother with a synthetic or blend. I'd go with good ol' conventional 10w-30.
Yeah I have looked into the process of changing the rear main seal, but its such a slight leak that I'm not really worried about it. Also like you said it's possible that its coming from somewhere else and just dripping there, until the leak gets worse I'm not very concerned with it.
Shell Rotella 10W30 Syn blend , 5-6k oci
Check the oil pan bolts where the exhaust is closest to. The heat tends to make them loosen and it looks like a rear seal leak
Originally Posted By: Miller88
Originally Posted By: WMW0505
I put nearly 200,000 miles on a Cherokee with a 4.0L I-6 and AW-4 auto using a wix 51515 and Mobil Clean 5000 10W-30 (now Mobil Super 5000?). Did an annual drain and fill on the ATF in both the AW-4 and NP231. OCI was 5,000 miles.
Sold it a few years ago and it was still running like a top. No clue where it is today.
Edit: I also had a very small leak from the rear main. Never fixed it because it wasn't enough to even see a drop on the dipstick between changes. But, from what I read the rear main on the 4.0 is pretty easy. Only the pan has to be dropped, transmission does not have to be pulled. Don't know from first hand experience though. So if you wanted to run synthetic you could just fix the rear main seal.
Depends on the model for the rear main seal. Changing the seal itself is relatively easy, but getting the oil pan off is the hard part. On a TJ Wrangler , the exhaust flows forward and under the oil pan , so part of the exhaust has to come off. On a Cherokee all you really have to do is maneuver it around the front axle.
The newer 4.0Ls don't really have the rear main seal problems that the older ones had. The way the engines are oriented in the vehicle, any leaks will run towards the back of the enginee and down the back of the block. Unless it's coming out of the starter or the bellhousing, I'd lean more towards an oil pan gasket, valve cover or oil filter housing adapter. A lot of people get diagnosed and pay for a rear main seal replacement, and their jeep does stop leaking ,but it was the oil pan gasket that was the problem the whole time.
But for a 3000 mile oil change interval I wouldn't even bother with a synthetic or blend. I'd go with good ol' conventional 10w-30.
I forgot the wrangler and Cherokee 4.0 had different exhaust set up.
I agree, if you can live with the leak just run a good conventional 10W-30 and good filter for 3,000-5,000 miles.
How many miles do you have on your XJ? I miss mine and have been close to picking another one up lately.
Originally Posted By: WMW0505
I put nearly 200,000 miles on a Cherokee with a 4.0L I-6 and AW-4 auto using a wix 51515 and Mobil Clean 5000 10W-30 (now Mobil Super 5000?). Did an annual drain and fill on the ATF in both the AW-4 and NP231. OCI was 5,000 miles.
Sold it a few years ago and it was still running like a top. No clue where it is today.
Edit: I also had a very small leak from the rear main. Never fixed it because it wasn't enough to even see a drop on the dipstick between changes. But, from what I read the rear main on the 4.0 is pretty easy. Only the pan has to be dropped, transmission does not have to be pulled. Don't know from first hand experience though. So if you wanted to run synthetic you could just fix the rear main seal.
Depends on the model for the rear main seal. Changing the seal itself is relatively easy, but getting the oil pan off is the hard part. On a TJ Wrangler , the exhaust flows forward and under the oil pan , so part of the exhaust has to come off. On a Cherokee all you really have to do is maneuver it around the front axle.
The newer 4.0Ls don't really have the rear main seal problems that the older ones had. The way the engines are oriented in the vehicle, any leaks will run towards the back of the enginee and down the back of the block. Unless it's coming out of the starter or the bellhousing, I'd lean more towards an oil pan gasket, valve cover or oil filter housing adapter. A lot of people get diagnosed and pay for a rear main seal replacement, and their jeep does stop leaking ,but it was the oil pan gasket that was the problem the whole time.
But for a 3000 mile oil change interval I wouldn't even bother with a synthetic or blend. I'd go with good ol' conventional 10w-30.
I forgot the wrangler and Cherokee 4.0 had different exhaust set up.
I agree, if you can live with the leak just run a good conventional 10W-30 and good filter for 3,000-5,000 miles.
How many miles do you have on your XJ? I miss mine and have been close to picking another one up lately.
Originally Posted By: Chris142
Check the oil pan bolts where the exhaust is closest to. The heat tends to make them loosen and it looks like a rear seal leak
The 3 next to the exhaust on mine weren't even finger tight. Probably another 1000 miles and I would have lost one or two of them. Whoever had the oil pan off ... it was a rubber gasket, not factory cork, didn't tighten them.
Originally Posted By: WMW0505
I forgot the wrangler and Cherokee 4.0 had different exhaust set up.
I agree, if you can live with the leak just run a good conventional 10W-30 and good filter for 3,000-5,000 miles.
How many miles do you have on your XJ? I miss mine and have been close to picking another one up lately.
Going to hit 206K by the end of the month
It's tired and has lived a rough life, though. Mostly an off road toy and serves as my truck currently so it has to tow. Lift, bigger tires, locker and a winch.
Check the oil pan bolts where the exhaust is closest to. The heat tends to make them loosen and it looks like a rear seal leak
The 3 next to the exhaust on mine weren't even finger tight. Probably another 1000 miles and I would have lost one or two of them. Whoever had the oil pan off ... it was a rubber gasket, not factory cork, didn't tighten them.
Originally Posted By: WMW0505
I forgot the wrangler and Cherokee 4.0 had different exhaust set up.
I agree, if you can live with the leak just run a good conventional 10W-30 and good filter for 3,000-5,000 miles.
How many miles do you have on your XJ? I miss mine and have been close to picking another one up lately.
Going to hit 206K by the end of the month
Yeah when I was jeep shopping I knew I wanted a 4.0 because of its tough reputation. Mine is a Sahara and has the D44 with optional 4:10 gears and rear disc so it has plenty of torque and is a fun around town vehicle. Doesn't see much highway use, that's what the wife's camry is for.
Originally Posted By: The Shape
I have a 2004 Jeep Wrangler with the 4.0. I bought it last year with 73K miles on it. My first oil change I went with mobile full synthetic 10W-30 because that is the brand oil I have used for years now in my vehicles. It might be in my head but the slight leak at me rear main seal seemed to drip more after the oil change, so next change I switched to the mobile 5000 conventional oil with a mopar filter and the rear barely seems to drip. I have been doing an old school 3K OCI. How does this sound? Advice on oils or OCI???
Congratulations, you've got one of the best engines of the last 50 years, although certainly not one of the fastest or most powerful. They're not terribly picky about oils, and they're very old-school in design- flat-tappet cam/lifters are the main design features that affects the oil requirement. Normally that kind of cam/lifter interface needs an oil with a lot of ZDDP, but the valve springs are very light in the 4.0 (its never worth it to rev it above 4000 anyway) and the cam profile is mild, so once its broken in, pretty much any modern, quality oil will do. Conventional or synthetic, doesn't matter.
Personally, I'm one of the ones that believes the 4.0 works just a little better using a 40-weight oil over a 30, although I've run both. I typically run Rotella T6 5w40 with a minimum 6000 mile interval. I also run a PH-8A sized filter (I actually use either a Royal Purple or Fram Ultra), and those could easily go 12000 miles between changes.
Others mentioned the rear main seal, and those do tend to weep. But the bigger likely leak source is the O-ring behind the right-angle oil filter adaptor, or the valve cover. I just had my daughter's '99 re-gasketed this past summer at a little over 175k miles, and its back to being completely dry. It had gotten to the point it would leave a 2" diameter spot on the concrete overnight from a combination of the oil filter adaptor, rear main, and valve cover. Rotella T6 didn't leak any more than conventional 10w30, but I did run an OCI of M1 5w40 TDT that might have leaked a few drops more every night. Maybe just imagination.
I have a 2004 Jeep Wrangler with the 4.0. I bought it last year with 73K miles on it. My first oil change I went with mobile full synthetic 10W-30 because that is the brand oil I have used for years now in my vehicles. It might be in my head but the slight leak at me rear main seal seemed to drip more after the oil change, so next change I switched to the mobile 5000 conventional oil with a mopar filter and the rear barely seems to drip. I have been doing an old school 3K OCI. How does this sound? Advice on oils or OCI???
Congratulations, you've got one of the best engines of the last 50 years, although certainly not one of the fastest or most powerful. They're not terribly picky about oils, and they're very old-school in design- flat-tappet cam/lifters are the main design features that affects the oil requirement. Normally that kind of cam/lifter interface needs an oil with a lot of ZDDP, but the valve springs are very light in the 4.0 (its never worth it to rev it above 4000 anyway) and the cam profile is mild, so once its broken in, pretty much any modern, quality oil will do. Conventional or synthetic, doesn't matter.
Personally, I'm one of the ones that believes the 4.0 works just a little better using a 40-weight oil over a 30, although I've run both. I typically run Rotella T6 5w40 with a minimum 6000 mile interval. I also run a PH-8A sized filter (I actually use either a Royal Purple or Fram Ultra), and those could easily go 12000 miles between changes.
Others mentioned the rear main seal, and those do tend to weep. But the bigger likely leak source is the O-ring behind the right-angle oil filter adaptor, or the valve cover. I just had my daughter's '99 re-gasketed this past summer at a little over 175k miles, and its back to being completely dry. It had gotten to the point it would leave a 2" diameter spot on the concrete overnight from a combination of the oil filter adaptor, rear main, and valve cover. Rotella T6 didn't leak any more than conventional 10w30, but I did run an OCI of M1 5w40 TDT that might have leaked a few drops more every night. Maybe just imagination.
Originally Posted By: The Shape
Cool I'll take a look at that O ring. Also I said it had 4:10 gears, not sure what I was thinking it has 3:73 gears
Easier said than done, in some chassis. Its retained with a gigantic Torx-head bolt, and is really, really close to the unibody rail in the XJ. Not sure about your TJ.
Cool I'll take a look at that O ring. Also I said it had 4:10 gears, not sure what I was thinking it has 3:73 gears
Easier said than done, in some chassis. Its retained with a gigantic Torx-head bolt, and is really, really close to the unibody rail in the XJ. Not sure about your TJ.
Originally Posted By: Miller88
Originally Posted By: Chris142
Check the oil pan bolts where the exhaust is closest to. The heat tends to make them loosen and it looks like a rear seal leak
The 3 next to the exhaust on mine weren't even finger tight. Probably another 1000 miles and I would have lost one or two of them. Whoever had the oil pan off ... it was a rubber gasket, not factory cork, didn't tighten them.
Originally Posted By: WMW0505
I forgot the wrangler and Cherokee 4.0 had different exhaust set up.
I agree, if you can live with the leak just run a good conventional 10W-30 and good filter for 3,000-5,000 miles.
How many miles do you have on your XJ? I miss mine and have been close to picking another one up lately.
Going to hit 206K by the end of the month
It's tired and has lived a rough life, though. Mostly an off road toy and serves as my truck currently so it has to tow. Lift, bigger tires, locker and a winch.
Awesome. Mine was stock when I bought it. When I sold it I was running 33x12.50's, front auto locker, and 4.56:1 gears. I replaced the 8.25 rear end for a Dana 44 from another XJ.
Mine took a lot of abuse too, looking back I'm extremely impressed it held up as well as it did.
I've only been looking at stock ones so far, not many left in decent shape.
Are your 206k miles adjusted for larger tires? You might have well over that if many of those miles were on tall tires.
Originally Posted By: Chris142
Check the oil pan bolts where the exhaust is closest to. The heat tends to make them loosen and it looks like a rear seal leak
The 3 next to the exhaust on mine weren't even finger tight. Probably another 1000 miles and I would have lost one or two of them. Whoever had the oil pan off ... it was a rubber gasket, not factory cork, didn't tighten them.
Originally Posted By: WMW0505
I forgot the wrangler and Cherokee 4.0 had different exhaust set up.
I agree, if you can live with the leak just run a good conventional 10W-30 and good filter for 3,000-5,000 miles.
How many miles do you have on your XJ? I miss mine and have been close to picking another one up lately.
Going to hit 206K by the end of the month
Awesome. Mine was stock when I bought it. When I sold it I was running 33x12.50's, front auto locker, and 4.56:1 gears. I replaced the 8.25 rear end for a Dana 44 from another XJ.
Mine took a lot of abuse too, looking back I'm extremely impressed it held up as well as it did.
I've only been looking at stock ones so far, not many left in decent shape.
Are your 206k miles adjusted for larger tires? You might have well over that if many of those miles were on tall tires.
Originally Posted By: The Shape
I have a 2004 Jeep Wrangler with the 4.0. I bought it last year with 73K miles on it. My first oil change I went with mobile full synthetic 10W-30 because that is the brand oil I have used for years now in my vehicles. It might be in my head but the slight leak at me rear main seal seemed to drip more after the oil change, so next change I switched to the mobile 5000 conventional oil with a mopar filter and the rear barely seems to drip. I have been doing an old school 3K OCI. How does this sound? Advice on oils or OCI???
Mobil Super High Mileage 5k or 6 months that's the mobil guarantee, sounds the way to go and I'm am doing that on my son's 4.0 Cherokee this weekend with a Mopar MO-90 OIL FILTER.
TOTO.
I have a 2004 Jeep Wrangler with the 4.0. I bought it last year with 73K miles on it. My first oil change I went with mobile full synthetic 10W-30 because that is the brand oil I have used for years now in my vehicles. It might be in my head but the slight leak at me rear main seal seemed to drip more after the oil change, so next change I switched to the mobile 5000 conventional oil with a mopar filter and the rear barely seems to drip. I have been doing an old school 3K OCI. How does this sound? Advice on oils or OCI???
Mobil Super High Mileage 5k or 6 months that's the mobil guarantee, sounds the way to go and I'm am doing that on my son's 4.0 Cherokee this weekend with a Mopar MO-90 OIL FILTER.
TOTO.
Originally Posted By: WMW0505
Originally Posted By: Miller88
Originally Posted By: Chris142
Check the oil pan bolts where the exhaust is closest to. The heat tends to make them loosen and it looks like a rear seal leak
The 3 next to the exhaust on mine weren't even finger tight. Probably another 1000 miles and I would have lost one or two of them. Whoever had the oil pan off ... it was a rubber gasket, not factory cork, didn't tighten them.
Originally Posted By: WMW0505
I forgot the wrangler and Cherokee 4.0 had different exhaust set up.
I agree, if you can live with the leak just run a good conventional 10W-30 and good filter for 3,000-5,000 miles.
How many miles do you have on your XJ? I miss mine and have been close to picking another one up lately.
Going to hit 206K by the end of the month
It's tired and has lived a rough life, though. Mostly an off road toy and serves as my truck currently so it has to tow. Lift, bigger tires, locker and a winch.
Awesome. Mine was stock when I bought it. When I sold it I was running 33x12.50's, front auto locker, and 4.56:1 gears. I replaced the 8.25 rear end for a Dana 44 from another XJ.
Mine took a lot of abuse too, looking back I'm extremely impressed it held up as well as it did.
I've only been looking at stock ones so far, not many left in decent shape.
Are your 206k miles adjusted for larger tires? You might have well over that if many of those miles were on tall tires.
I never changed the speedo gear for the bigger tires. So I'm putting more miles on it than I think I am. I have a front lunchbox in it, swapped in high pinion dana 30 since the low pinion dana 30 self destructed. Some day, it'll get 4.10 or 4.56 gears and a ford 8.8 rear end with disc brakes.
Many plans. This one I would like to turn into full time trail vehicle and get another unmodified one and keep it that way!
Originally Posted By: Miller88
Originally Posted By: Chris142
Check the oil pan bolts where the exhaust is closest to. The heat tends to make them loosen and it looks like a rear seal leak
The 3 next to the exhaust on mine weren't even finger tight. Probably another 1000 miles and I would have lost one or two of them. Whoever had the oil pan off ... it was a rubber gasket, not factory cork, didn't tighten them.
Originally Posted By: WMW0505
I forgot the wrangler and Cherokee 4.0 had different exhaust set up.
I agree, if you can live with the leak just run a good conventional 10W-30 and good filter for 3,000-5,000 miles.
How many miles do you have on your XJ? I miss mine and have been close to picking another one up lately.
Going to hit 206K by the end of the month
Awesome. Mine was stock when I bought it. When I sold it I was running 33x12.50's, front auto locker, and 4.56:1 gears. I replaced the 8.25 rear end for a Dana 44 from another XJ.
Mine took a lot of abuse too, looking back I'm extremely impressed it held up as well as it did.
I've only been looking at stock ones so far, not many left in decent shape.
Are your 206k miles adjusted for larger tires? You might have well over that if many of those miles were on tall tires.
I never changed the speedo gear for the bigger tires. So I'm putting more miles on it than I think I am. I have a front lunchbox in it, swapped in high pinion dana 30 since the low pinion dana 30 self destructed. Some day, it'll get 4.10 or 4.56 gears and a ford 8.8 rear end with disc brakes.
Many plans. This one I would like to turn into full time trail vehicle and get another unmodified one and keep it that way!
For cars with small oil leaks, I prefer to use a high mileage oil. My preferred high mileage oil is Valvoline Maxlife.
- Status
Similar threads
