Late last year I purchased a 2018 F150 with the 2.7L V6. My initial mileage (according to the computer) reached a max of 23.7 and then slowly started going down and leveling off at 21.2 or so. As an experiment, I've now run about 25 gallons of premium through it and the mileage has climbed back to 21.9. According to most every info site I can find, premium isn't known to be of any benefit increasing MPG yet there it is. I have a 500 mile round trip planned next week as my final test to see how close I can get back to the 23.7 I started with. Now I have not bothered with the math to determine at what point fuel at .30 cents /gal more is a benefit but have to wonder if it's just a better choice for the engine overall? I don't tow anything, it's just a 4WD passenger vehicle 99% of the time. There must be some reason the engine is responding positively to premium?