[hat_man]

Had a near record tank going and then the wife says she wants to take the truck on date night. She likes her air conditioning and in this heat I wasn't risking making date night into an argument so AC it was.

I figured it was going to drop the MPG numbers pretty good but surprisingly, it didn't move them much at all. Hmmmm........

I know that windows down and AC off at highway speeds is supposedly the same as windows up and AC on at highway speeds, but I usually run windows cracked AC off/vents on at highway speeds, and have been getting stellar mileage. This tank the mileage wasn't that different.

So the question is this......

Was it just the fact that date night was only the last 90 miles of a 450 mile tank and I only paid a minor penalty, and it was really going to be a record tank?

Or...........did the extra drag on the engine from running the AC cause me to step into the gas pedal slightly harder (more engine load), negating some of the pumping losses from running with such a light foot? (I hope I have that concept right?)

I guess the real way to tell is drive to work in the cool mornings with the windows cracked like always, and then roll them up and run the AC every day on the way home and see how the tank compares. This week should be a good week for an experiment with temps in the 90's and heat indexes over 100 until this weekend.