$0.279 in Florida in 1972. Average price everywhere else was in the mid- to high-30s/gallon. Price war.
My father clearly remembered 15 cents/gallon in 1961 (my year of birth) at the Navy PX station at Lakehurst, NJ. Not available to civilians, though.
Now I see $1.749 at a local Sam’s Club (San Antonio). Adjusted for inflation, it is comparable to late ‘60s prices, and cars get better mileage now even with all of the heavy and restrictive safety and emissions crap. So cost per mile, adjusted for inflation, is probably about as low as ever (certainly for most people still breathing, though many Dem voters will remember lower prices :>) ).
FYI, I found a great inflation calculator at http://www.bls.gov/data/inflation_calculator.htm
$1.75/gallon now is equivalent to $0.26/gallon in 1968, the year my father got our 1969 GTO. Premium at that same station is now $2.19, equivalent to $0.32 in 1968 (and I remember Dad paying about $0.37 for premium then).
Note that my father’s GTO got maybe 15 mpg on the highway under ideal conditions. Compare/contrast to a typical (much faster and better handling) muscle car of today, which gets say 22 mpg highway: GTO - 2.4666 cents/mile; 2015 muscle car 1.4545 cents/mile, inflation adjusted.
Folks, TODAY is the good old days for gasoline cost per mile.