I have a 1999 EX Saloon A/T with 150T on the odo. I use full synthetic oil and Petron E10, so far I estimate it to consume about 9 to 10 km per liter (mix city and highway driving). Considering the age of the car I think the gas consumption is acceptable.

Overall, the maintenance cost of a Nissan Sentra is low. Its my third sentra and so far none have broken down on me.