I get 16 miles per gallon, on 87 and 13-15 miles per gallon, on 93? I thought the higher the octane the higher the milage. My driving route has been the same eveyday for over a month. College M-F, Work Sat and Sun. Haven't had time to just cruise around. Traffic is the same, the speeds are the same. Ever since I had my engine rebuilt I've run 93, but since I'm a broke college student again, I've been running 87 with 30 miles more per tank. Can someone educate me, thanks.

 

87 has more calories or heat energy than 93. 93 will chemicaly retard your timing.