I've got it, seems to vary based on brand of fuel and outside air temperature.

 

My '09 6speed rattles like a tin can full of marbles when under load if I use regular unleaded; runs like a dream on mid or high octane premium & gets better mileage.

Fact is, I shouldn't have to pay the extra $8 bucks a tank for my Jeep to run adequately if Chrysler claims (as they do) that low octane gas is sufficient. It's not like the JK's running a Corvette motor or anything. Anyway, love my Jeep so I just suck it up & pay the extra for gas.

 

Just had my 2008 in for new bearings and crankshaft! how the heck does something like that happen in a two year old engine!!!!!!

 

My mid year 2008 went in for knock at idle (even on cold start), although it was not noticeable once you were driving. Anyway, they said something about the rods or bearings and bad lifters and tappets. I got a ton of headwork done and a whole new shortblock under warranty. It runs awesome now!

 

I've definitely been noticing more and more of this myself. It only seems to happen everyonce in a while though. It's usually when I get up to about 2600rpms or slightly higher going up hill or trying to pass someone. Sometimes it's worse than others....

I have an '08 unlimited btw 31k miles

 

I have a 2010 unlimited with 20K miles. Using 87 octane it'll ping some uphill, especially if loaded with people & stuff. Goes away if I keep the RPMs high (above 3K).

I'm trying a tank of 87 w/a bottle of techron. After I see what that does, maybe a tank of 89 octane.

I'm noticing some increased oil consumption too and have read all the threads on that. It's used about 1/2qt during first 1000 miles since last oil change. "Normal" as Chrysler says.

After I track the pinging and oil use over the next few months, I'll take to the dealer.

I love driving the jeep, but want to make sure the engine and tranny are healthy before the 5yr/100K warranty expires.