i average about 16mpg combined driving give or take about 10% depending on traffic patterns. the only change ive made from stock is a k&n and mobil 1 oil. i use "plus" grade gas (89 ) more to ensure i get cleaner gas than for the octane rating (for the extra $2 a tank its well worth it to me.) im tuned to factory specs....check my tire pressure regularly ( this can make a big difference) , etc... and i generally drive fairly hard , i think i could do better if i babied it , but the vx seems to like to be pushed a bit..