Hello people, so i noticed my 2004 g35 has been emitting grey smoke from time to time and I'm looking for the possible causes. I've tracked the situation and here's what i found.

Situations when it smokes:
- After going uphill, when going downhill: constant smoke
- After idling when I gas it a little a cloud comes out, but after that nothing at all.

About my car:
- It has a single exit exhaust with the catalytic converters present but no stuffing.
- I've noticed no coolant level decrease at all, and no oil level decrease at all.
- Car drives like a charm and I don't beat it that often.
- Changed the valve covers not long ago cuz they were leaking oil, nothing else.

You can see an example here:

 

If you have time check for more oil leaks at some point in combustion cycle you are cooking off fluid from a leak. Gauge for coolant temp wouldn’t really be an immediate indicator. Only because you can loose a lot in small quantities gradually and get white smoke for burning oil and/or coolant.