We were a little underwhelmed by the results of our first dyno session last Thursday, so we ran the tank pretty close to dry and refilled it with nearly 18.5 gallons of 93 Octane Chevron, then drove another 50 miles to make sure the engine computer had time to "learn" that it had higher octane fuel in it. As you can see in the plot below, it appears that this higher octane fuel allowed the engine computer to take advantage of the extra octane as both torque and horsepower improved between 5400 and 6600 rpms, with maximum gains of around 8-9hp and between 6 and 7 lb-ft of torque. Are the gains worth spending an extra $3-4 per tank? Probably not.