Recently I've been reading about a lot of posts about severe engine problems occuring in the Jeep around the 40,000 mile mark. I wanted to get a poll going to see how many people have had this issue, and if there might be a factor that links some of the issues together.

If you have between 30,000 and 50,000 miles on your vehicle, post whether or not you have engine issues or warning signs, how often you change your oil, what oil weight you use, any engine mods (CAI, tuning, etc), and any other factors that might be related.

Micah

 

No issues for me and I have 58,000 on my 2008. I'm using Amsoil 5w-20.

 

No issues here either - almost to 36K miles; been using Motorcraft 5W20 Synthetic since I bought it in February last year (previous owner had the oil changes done at the dealership). Oil changes every 3 - 6 months or 3,000 - 5,000 miles; so far, I've been going off the miles since I put 3,000 miles before I get to 3 months . Nothing by way of engine mod; running a Hypertech programmer primarily to correct my speedometer. So far, it looks like 11 people have answered the poll with an astounding 100% on the "No issues".

 

Poll didn't have my option, so I put what your intent was. I've used Mobil1 or other synthetic since about 600 miles. Up to 40K on speedometer now (not quite accurate due to tires).
My water pump failed, but that had nothing to do with the oil. I historically used Mobil filters, but have recently changed to Mastercraft because the filter valve issues.

 

30K miles, no issues at all (motor runs smoother now than it did when I got it).

Change oil every 3000mi with 5w30 full-synthetic (Castrol Edge) & Mopar filter.

I run the heavier weight oil because it's hot where I am & the motor doesn't use any oil between changes, but it did when I used 5w20 (suggesting it was too thin & being burnt; oil also got a lot blacker more quickly on the 5w20). The motor also runs noticibly smoother and quieter on the heavier weight oil when revved above 3000RPM and appears to have more power, suggesting improved compression.

I too am paranoid about reports of crank bearing issues on the JK so am being careful; I always let it warm up from cold before driving it to let the oil reach operating temperature before putting the motor under load. If I must rev it above 3500RPM for sustained periods (ie; long hill climbs) I'll do it in a lower gear with reduced throttle to reduce the load on the rods & bearings. I know it's silly to have to carry on like this with a new vehicle (it's usually how I treat on old car with 200K miles on the clock in order to squeeze a few extra years of life out of it) but I cannot affort to replace my JK's motor if it fails prematurely.

 

Used 5W20
No Mods other than Flashpaq
Changed oil every 4k miles

Spun number one Main Bearing @ 45k miles. Damage to crank, journals, who knows how much metal went through the engine. Hopefully the filter caught it all. In the process of tearing the engine out and getting a look inside.

I know those of us that have had similar issues with engine problems are WAY in the minority, but it is a shame that Jeep didn't stick with the 4.0L Straight 6. I realize that no other Chrysler vehicle used that motor, but it was just about bullet-proof.




Anthony

 

I have had no engine issues other than under powered. I use 0w20 high mileage Mobile One synthetic. I average 15 mpg with 28000 miles on the odometer. I think the stock 4:10 rear end has helped the low mpg. Reliability has been excellent.

 

No problems here, I am at 34000 and use Mobile1 5w-20 since new, I change between 5k-7k miles.

 

07 50k miles. Used up to 3 qts. between changes (3k). Now uses about a qt. Had dealer look at it,water pump replaced, broken exaust manifold bolts replaced,oil changed to 5w30. Alls well!

 

31k miles, 5w20 every 3000 miles like clock work. It'll use a li'l oil between changes... no more than a quart. Have people been switching to 5w30?