I have found it good to shop around a bit. I know 3 stations I like in my areas. One where I work that sells large quantities of fuel, one near home that says it's fuel is premium (though I like this one the least), and one I visit once a week that sells B5. I've tried many others, and these three yielded the best fuel economy, the least smoke and especially the B5, the most user satisfaction (other lesser variables that can be dropped into one value).
Find a station you like most. Look for good fuel economy from it, no noticable smoke, and many customers (fresher fuel)