Hello, I'm new to the forum and to owning a G35.
I bought mine as a back up vehicle and I've only drove it a couple times. Here's the problem: The oil appears fine before it's running, but during it has a white milky appearance towards the top of the dipstick as you can see in the image. The coolant disappears pretty fast and I just assumed it leaked before but now I'm worried about it being the head gasket. Is it possible this is just condensation built up in the oil? The odo reads 240,000

 

well, disappearing coolant + milkshake in the oil is not good news. can you lift the car and see if you notice any coolant stains/leaks there? my water pump went around 250k and was leaking by the a/c compressor. the seals were shot on that thing, but no coolant was mixing yet. since the WP has both the oil and coolant seals, it *could* be your water pump, but would need further inspection. is it blowing smoke out the tail pipes when you drive it? grab a second car and have it follow you around to confirm that.

 

If it's drinking coolant then you should be able to SPOT the leak if it's external, otherwise, most likely water pump o-rings that pass through the front timing chain area.
But, if it was internal mix, you would see A LOT of milk inside, not just a smidge. The oil looks old, did the car sit for a LONG time?

 

Thanks for your replies, it sat basically since last summer I barely drove it. It is just condensation thankfully I had my mechanic check it out since I haven't had time. Head gasket is still good 👍

 

good news, but you still need to figure out where that coolant is going. you can rent a pressure tester from AZ and hook it up to see if it's an external leakage.