I just picked up a cherry 95 sport I-6. It has 98k on the clock. The rear main is weeping a bit. Can I run a thicker oil to slow the leak?? It calls for 10w-30, but with higher miles I am hopping to find out what is the thickest oil I can use in the winter. Thanks in advnace.
Jeep oil reccommendations
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Delo 400 15w40 and Mobil 1 Delvac 15w40 both come highly recommended for the bulletproof I6. They are both heavy duty engine oils, typically used in diesel applications, and they both appear to work VERY well in our ancient engine design.
98K isn't really high mileage for a 4.0 but the high mileage oils are thicker than normal, and have seal conditioners. I've had good results with the Chevron/Havoline versions, they're not expensive, but excellent. Gary likes Rotella 5W40.
What part of the east coast are you on? Florida winters are abit different from Maine, you know?
You might want to do an Auto-Rx treatment or two, it would clean up the insides, and may stop the leak too.
What part of the east coast are you on? Florida winters are abit different from Maine, you know?
You might want to do an Auto-Rx treatment or two, it would clean up the insides, and may stop the leak too.
If you do look at UOA's you can find plenty with 10W30 that show good results, several are better than 40 weight oils, depends on your situation.
The high mileage oils are typically about 12 cST @100C. I'd give one of them a shot at the leak, or Auto-RX, before thinking about a seal change.
The high mileage oils are typically about 12 cST @100C. I'd give one of them a shot at the leak, or Auto-RX, before thinking about a seal change.
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How are you intending to drive this jeep? Winter weekend warrior? Daily 25 mile commuter? Around town frozen dinner getter (you can't fit many groceries in it)?
You can use just about anything. If you're going to leave it in for a decent OCI, use a 10w-30 over a 5w-30 to avoid shearing, but it won't be a factor if you have a 6 mile commute - even a 20 weight is probably still a 40 weight due to temp over that duration of running. If you do longer commutes, I'd go with a 40 weight. If you do longer OCI's, I'd recommend a synth.
You can use just about anything. If you're going to leave it in for a decent OCI, use a 10w-30 over a 5w-30 to avoid shearing, but it won't be a factor if you have a 6 mile commute - even a 20 weight is probably still a 40 weight due to temp over that duration of running. If you do longer commutes, I'd go with a 40 weight. If you do longer OCI's, I'd recommend a synth.
I am in CT. Does the thicker weights kill the fuel economy at all?
Fuel economy and 4.0L don't go in the same sentence 
oke: I'm your neighbor right over the border from Union,CT.
I usually run 10W40 in my 2.5L YJ. I change it every 1000 miles or so as it is a trail only Jeep and is beaten regularly. For winter, I like Castrol 5W30. It's 10.8cST @100*C which is a decent 30wt when warmed up.
Run a search on 4.0L or Jeep in the UOA section and you'll see that this design of engine enjoys a thicker oil.
A rear main seal is cheap for your 4.0L and is easy to do. I've done a few for friends and it take about 1-2 hours.
Happy Trails.
oke: I'm your neighbor right over the border from Union,CT. I usually run 10W40 in my 2.5L YJ. I change it every 1000 miles or so as it is a trail only Jeep and is beaten regularly. For winter, I like Castrol 5W30. It's 10.8cST @100*C which is a decent 30wt when warmed up.
Run a search on 4.0L or Jeep in the UOA section and you'll see that this design of engine enjoys a thicker oil.
A rear main seal is cheap for your 4.0L and is easy to do. I've done a few for friends and it take about 1-2 hours.
Happy Trails.
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I would use either Pennzoil or Castrol High Mileage in 10W-30. Do two OCIs to see if it improves. Limit your OCIs to 5K.
I have a 94 XJ Sport with the 4.0 W/ 158,xxx on the clock. I run Rotella 15w-40 in the summer and Mobil1 5W-40 T&SUV in the winter.
I'd run a quality 10W30 in it. I used to run (and recommended) Mobil Delvac 1300 15W40 in mine and have since switched permanently to Mobil 5000 10W30. With the 10W30 it turns over faster, idles quieter and the mpg has picked up a little bit. The Mobil 5000 10W30 is also diesel rated, so it's a robust oil and a great bargain at less than $2 a quart.
Edit-As for the rear seal, pretty much all 4.0s will have a leaky rear main at some point...I wouldn't worry about it unless it's a dripper.
Edit-As for the rear seal, pretty much all 4.0s will have a leaky rear main at some point...I wouldn't worry about it unless it's a dripper.
My 2001 GC with the I6 has been on a steady diet of Rotella Synthetic 5W40 for a while. No problems, no leaks, no noise at startup. In the winter I throw in a quart of 5W20 (now that my stash of M1 0W30 is used up) and then fill with the Rotella. 19-20 mpg mixed city/highway and we'll crack 25 mpg on the interstate if I keep my foot out of it. 16 mpg towing a 3700 lb trailer at 65-75 from Tampa, FL to Charlotte, NC.
Best part is the gallon jugs are easy to handle for toting oil back to Autozone.
Best part is the gallon jugs are easy to handle for toting oil back to Autozone.
My 95 JGC with a 4.0 L engine ran wonderful for the 197,000 miles I owned it. I ran Mobil 1 10w30 with a PureOne oil filter from the first change at 2,000 miles.
Using 0W-40 Esso XD-3 synthetic year round in both my Jeeps with either a Baldwin or Napa Gold Ford oversize...they use no oil,leak no where and start/run great in any weather.Too bad you yanks can't get this oil
My roommate runs Rotella T 5w40 in his 2004 Jeep XJ Rubicon, based on my recommendation after reading the UOA's on this forum.
Would the 5w-40 work in Southern Illinois where temps get down to about 0 for a week or so at night? The manual calls for 10-30.. It sometimes gets about 32f even in January..
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