I've managed to put 4k miles on without any new issues other than trying to open the glovebox. The handle disintegrated into pieces and the lock fell out. Oh well. Always always always jumps into limp mode until car hits operating temperature. Restarting after hitting temp it works as it should. Smooth and quite. Now at 105k and its using a quart of oil every 2k miles. No smoking, smells or visible leaks except for a tiny spot on the bell-housing. Pretty much stopped the trans leak too. Again maybe a drop but I have to go looking for it too. Nothing on the cardboard under the car Also in that 2k period it empties the coolant container to the point it triggers the red warning light. I purposely let it go this low to get an idea how long it takes to empty out or almost empty. Not doing that anymore but now I know. No visible leaks, no coolant smells either, just a continuous loss hidden away under the intake manifold. Never did pinpoint it other than above and forward of the transmission. After adding some sealant at 101k the obvious smell disappeared and never came back. Someday somewhere something will pop in that doomsday valley where the octopus hose and all its tentacles are reaching out desperately trying to snag my wallet. Until then I drive with an eye on the temperature guage and a valid membership to my local AAA autoclub. I never venture past the 200 mile towing range. Worst case it ends up in my driveway as a parts car.

​​​​​​​Still has that always on warning light for the defunct upper driverside O2 ssensor. The one you read about but can't touch or see. Not at the same time anyway. No idea how long it's been bad. Ever since I've known about the car so roughly in the early 90k rage. Runs like a top. Smooth quite idle and an exhaust that sells rich to my senses. Who knows. Given past experiences whatever i fix triggers a knew problem. Fixing nothing has proved to be cheaper. God only knows how long this machine keeps going. Oil, coolant and gas is all I'm willing to put into it. I'll never fully appreciate what this car was designed for. Being driven around enjoying the backseat roominess. As the driver i proceed with a caution foot on the gas. I-d love to floor it, open her up and feel the power but I fear that octopus under the hood will come reaching for my wallet while spewing out coolant. No need to ask for trouble. These cars do it voluntary. No coaxing needed. ​​​​​​​Richard T ​​​​​​​​​

 

Hmmm ... what version of the X308 are you writing about? I would reword one sentence to read, "God only knows how this machine keeps going."

 

Can you give us your car details?
What are the codes?
Have you done a coolant pressure test to find the leak?
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I would certainly recommend you replace the O2 sensor. The car will run much better once that is complete plus it's detrimental to the catalytic converter. Not a terrible replacement job but you'll need to remove the coolant tank and associated plumbing and heat shields to get access to the sensor.
As far as the oil consumption, I've had four XJ8's and they all burned oil at about that same rate so I'd consider it normal.