Hi, I do a lot of driving (I'm a courier) and want to improve my gas mileage, i average about 16-17 mpg, mostly city driving but i drive very conservatively. I have an 02 ranger, 3.0L auto. Any ideas how I can improve my MPG without spending too much money? Someone said their MPG went up from 23 to 28 using premium gas, is this really possible?

thanks