A "combat range" of 650 miles was 650 miles to target, 30 minutes of combat, and another 650 miles back to base -- somewhat better than 4mpg. However, the owner/flyer of the P-40E at War Eagles museum does cringe when he has the FBO fill the tanks, and the Allison engine does require 100/130 octane avgas. By the way, there are three fuel tanks; the total tank capacity is 156 gallons (some P-40 documents say 162.5 U. S. gallons).