In recent weeks several of the local convenience stores near where I live (NW side of Tucson) started creeping the price of low grade fuel down and ...down and down... Nothing really earthshaking as a percent of the whole bill - but best deal I got for my daily driver truck was at $2.19/gal. That was .30 less than the prices I saw on the southside.
Back in the last century, when I was pumping gas and wiping windows - and it was .30 and less per gallon - we used to sit a sign out at the curb (GAS WAR) and do the same sort of promotion. Wonder where the signs went............? 
Steve Metzger Tucson, Arizona