What is the best car to have for mpg?

im looking into buying a new car,,and im kinda swinging towards hybrids,,,i wanted to buy a hybrid cause the numbers it shows on the sticker which is 51 city and 48 highway,,,,but alot of people are telling me the ford fusion hybrid can go 1400 miles on a single tank and get just as much mpg as a prius can through the city despite it saying it only gets 38 city and 43 highway,,,,and others are telling me that diesel cars can get a upwards of 70 mpg through the city what car would be the best for me to get that i would spend less on gas a month