Welcome to the forum.
Exhaust manifiold cracks, generally drivers side under the heat shield, but sometimes passenger.
Also the manifold nuts back off.
Both of these cause exhaust leaks.
Also, these issues are 2007 to 2011, specific to the 3.8 engine.
It is also known to have issues with oil burning, leaks, etc. 5w-30 helps a lot with this.
Auto will be underpowered unless you get the Rubicon which has 4.10 gears. The auto trans in general is the main reason for it being called a "dog" though.
The 6 speed has issues of it's own, though it seems many times the cause is the factory didn't fully fill them. No real world experience in this part though.

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@Bobnh Thank you for your reply. I would be looking a manual transmission. Someone mentioned that they are not the greatest on fuel but didn't say any numbers as far as mileage per tank.

 

You do not get a jeep with fuel economy in mind. Stock you may get as advertised but I get around 14ish in my 08 jku with 37s/manual with stock 4.10 gears with bumper/skids/winch etc. Its a heavy pig-lol.

I just had engine done at 137k and on my 3rd clockspring but other than that the usual stuff.

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For comparison.
The 2007-11 3.8L / 4spd auto with 5.38 gears is the equivalent final drive to,
2012-18 3.6L / 5spd auto with 4.10 gears

• The 3.8L is a known high mileage engine but it was designed originally to run 10W30 oil. 5w30 is definitely better then 5W20. As for the oil burners by this time I would assume that all the bad ones have now been trashed and only the good ones are left. My 08 had 321,000klm on it when I traded it in.
• Exhaust manifolds are a thing but RIPP makes nice headers for the Jeep 3.8L.
• Engine ground straps tend to corrode and break causing some starting issues. Adding a 4gauge ground cable from the battery to the alternator fixes that issue.
• some report heater core issues, we had none with heater core or rad with any of our 3 3.8L Wranglers.
• because of the high transmission gearing with the auto, it is suggested that a external transmission cooler be added.

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@jeepjk1968 Thanks for you reply, I figured they were not going to be amazing on fuel, though l had a 95 Yj before and remember what that was like. I looked at "clockspring" and that as you mention seems to be a typical item that can cause issues.

 

The clockspring isn't the worst diy out there and after the first one rather simple-lol

I just get the random chime and airbag light.

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@JTPhoto JK Good to know regarding the ground strap, that seems like quite an easy fix. I suppose you are right when it comes to engine duration. The ones l have seen for sale all have what would be high mileage when comparing to the average car. I wonder what the highest recorded mileage on one of those engines is that still operates.

 

Welcome to the Forum, from Cave Creek AZ.

 

I have a 2010 JKU with the 6sp, 3.73, 35s. I get about 14 mpg overall. 16 on a road trip and that's averaging 70-75. 6th gear is basically useless unless it is downhill or flat. The 3.8 is a minivan motor, so it is built for durability not for speed. It does burn a little bit of oil but not excessive. First gear is good, but as soon as I shift to second even the bicycles are going by 🤣. Just replaced the heater core in mine because it plugged up, but it wasn't a terrible job.

 

I have a 2010 JKU with the 6sp, 3.73, 35s. I get about 14 mpg overall. 16 on a road trip and that's averaging 70-75. 6th gear is basically useless unless it is downhill or flat. The 3.8 is a minivan motor, so it is built for durability not for speed. It does burn a little bit of oil but not excessive. First gear is good, but as soon as I shift to second even the bicycles are going by [emoji1787]. Just replaced the heater core in mine because it plugged up, but it wasn't a terrible job.

A gear change will fix that. You would be surprised how much jam the 3.8 can have when properly geared and a programmer to tweak the performance.


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I have 2010 Sahara with 195K miles. Only major issue was a leaking heater core. I change oil every 5K miles with 10w30. I'm on a AEV 2.5" lift with 33s

Only other issue was oil pan leak, easy fix with new seal. That was at 160K miles

Still driving it as my DD