interesting fuel economy increase

[uchi]

this is kind of interesting, ive got an 09 sierra crew cab 4x4, when i got the truck i was getting about 15.5-16 mpg in the summer and thats with my wife driving it really gently. i was actually a little upset by this because it was the same if not a little worse than my 06 crew cab was getting and i bought this truck trying to get better mileage. then i tossed a trifecta engine and tranny tune into her. started to run 89 octane. the tune is meant for 91 but i didnt want to spend the extra money on 91 vs 89. regardless the power in crease was fantastic, the truck pulled hard, shifted hard, was great to drive. with regular doses of abuse the truck was seeing 15 mpg and 16.5 while driving it gently. with that kind of combo i didnt see the point in driving her easy. well the other day i topped up the top 1.3 tank with some 87, burnt through a half tank of gas, filled up last night and after the math she was showing 18.5 mpg. im guessing because the tune was adding timing, with the lower octane its pulling timing from it. theres a slight decrease in power but shes still peppy enough for my liking. im hoping to see a bit more of an increase once i dilute whats left into 87. just thought id share my findings

[ifshinxs]

Thats what I like to hear...More power and MPG.

[uchi]

that was last tank, this tank was all 87 and she showed me 14.8 mpg. and i drove her easy. towed a small load for maybe 40 km. no idea what happened there. next tank im going back up to premium. i was getting better mileage with 89 octane while beating the truck than i did on 87 driving it gently. if this is the pattern im seeing then ill jump to 91 next couple tanks and see what she reveals

[uchi]

tossed some 91 into the tank, after a day or so of running it i find the truck is very very happy with its current tune and the higher octane fuel. feels like its been tuned all over again