I've only had my G35 for a little over a week, so I personally really haven't experienced this yet, but in my old car ('02 Lexus IS300), I could definately feel a difference between a full tank and a near empty tank of gas. I also could tell a larger difference in performance between different temperatures. The performance difference between 60 degrees and 80 degrees (morning time and late afternoon) was very apparent.

 

Next time you fill your car up with gas you can actually watch your car get lower in the rear. I always thought my G felt peppy with empty tank of gas fill up your gas tank and it then has a slow reaction. I guess if you always want your G to perform and react well just put half a tank of gas ha,..

 

The warmer it is, the smoother it shifts...