I'd like to get a used JK unlimited, and my budget puts me in the 3.8L era. The specific one I'm looking at is a 2007 with 4.10 gears, which I assume will help with the butt-dyno. Assuming I test drive it and am OK with the power levels, how can I spot an oil-guzzling 3.8L? It's at a dealer, so I don't expect any knowledge of that history (or that it would be revealed if known). I'm not looking to spend $20K on a potentially bad engine.

Thanks for any warning signs or any other tips!

 

I'd shy away from the 07 since it was the first year and it seems like those are always...unique. I've not had any leaks but you'll find these motors consume more than they typically leak.

Check the fluids and see if they are where they should be and determine if it's new oil or if maybe it's been sitting a while. Hopefully with it being at a dealership they'd give you some sort of assurance.

 

I was sort of in the same boat. I looked around and found too many issues with the 2007, not to say it was a bad year or to flame current owners but it seemed to have more issues then others being a year one model. I myself went with a 2010 and have been happy.

 

I think you can do better than that for 20K I just bought a 2012 6 speed with 34 thousand on it for 22k granted ill have to do some regearing if I want to go nuts offroading but its not to bad just the way it is . Keep looking there are lots of jeeps out there ........... oops just saw it was a jku I still think you can do better considering that its got to have a ton of miles on it .

 

I the 07-08 era bring a code reader. There cheap and will so you if the dealership cleared any codes.(recommend for any car buying). Check the status of all the wires and shielding in the engine compartment. Also looks at the headers. There's a heat shield on them that blocks your view from a crack so if they looks old and rusty I would ask about that. Oil is a tough one listen for suttle pings and ticks( bring a long screwdriver and listen to every cylinder dealer will look at you crazy but hey better to know there's no abnormal pinging going on). Also look under the intake manifold just above the water pump for violent build up.( you see coolant it means it needs a new gasket) the oil consumption is going to be hit or miss they don't drip oil so it's almost impossible to tell until you drive it for awhile.

 

I drove a 2007 from August 3, 2007 until January 10th this year. I had no issues. It had 103,000 when I traded it in on my 2015. I probably should have kept it. It was a 2 dr Detonator X with 4.11 gearing. I kept the oil changed at 6,000 mile intervals. I did have a quart of oil magically disappear around 4 thousand miles into an oil change. My biggest concern on this used engines is that someone didn't mix the coolant. Those 3.8's take a different coolant than the 3.6 and if someone put the wrong stuff in there, it can cause some strange internal problems and leaking. Look closely at that tiny valley above the water pump in the front for a small (tiny) pool of mystery liquid. I would not have worried about keeping the one I traded because I bought it new. However, I would be worried about a used one I didn't know.

 

I wouldn't go with a 2007 and I can't believe they would sell for 22k.

I think the better years start at the late 08's and even better 2009 and 2010. No hard data to back it up, just my opinion. I own a 2008.

 

One thing that doesn't get talked about much is that some early 07's came with a D35 rear axle instead of a D44. Worth checking.

 

Yup. Only Rubi came with stock 44's front and rear. If it's a Rubi w/o 44's someone has built a phony.

 

This isn't correct. My 2007 X 2dr was built in July 07 and had a D44 rear and 4.11 gearing. Some of the very early 07's had the D35s.