I record every gas fill up since purchasing the Z with an app on the phone called fuel economy. The stats after 50633 miles are as follows;
Average mpg: 23 mpg
Best: 27.3
Worst: 18.9
Distance per fill: 380
Total fuel: 2227 gallons
Total cost:$12158.67
Cost/distance: $0.23/mile (including maintenance, tires, etc. )
Cost/fill up: $70.32
Average fuel cost: $4.22/gallon
Max cost: $5.56 (a little friggin gas station just outside of vegas.....f&@!kers)
Min cost: $2.71/gal
Yes, yes, I know I'm a bit OCD & anal retentive