When I was younger I was always in a hurry and challenged the posted speed limits. Retired for 13 years and on a fixed income, my driving habits have changed. Now I drive for dollars. It will take me as much as an hour longer on a 500-mile trip, but it is worth it. I admit that in a 55 MPH speed zone I still exceed the limit but never exceed 67 MPH, even in 70 & 75 MPH zones. On uphill slopes, I reduce my speed by as much as 5 MPH.

I own a 2015 Hyundai Hybrid. It is advertised as achieving 40 MPG on the highway. My average so far is just over 47 and I managed 49.6 on one trip. Saving 7 MPG over the 80,000 miles has saved us almost $1,000. I realize this is very low pay per hour of driving, but it pays for one vacation trip.

Other habits that I have developed is to accelerate very slowly from a stop and to look ahead for opportunities to avoid a full stop (like slowing down until the light turns green). According to my MPG meter rate of acceleration makes a significant difference. I also keep an eye on the MPG meter at all times.

Other factors that I have learned about economy: Driving in the rain will reduce mpg by as much at 15%. Gas quality makes a difference. On an identical RT to New Orleans (about 1,100 miles) but using different gas stations I got 48 mpg on one trip but only 44 on the other. I wish I could tell you which brand to use, the the better performance was from a non-brand station while the lesser was a well known brand. Another factor is the road service. A smooth asphalt surphase provides less friction (and road noise).

That said, the most significant factor is driving habit.