Optimal Cruising Speed for MPG

[gtman]

My cruising mpg numbers are consistently best at 55-60 mph. The real key to maximizing mileage at any cruising speed is maintaining minimal throttle and brake input. Basically that means highway cruising on a flat road with no traffic. In my case that never happens due to hills and extreme congestion and my tendency to want to go fast.

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[Florida_Frank]

Whether this plot is true is an additional issue. It suggests over 65 mpg when going 35-40 mph. Is this your experience? Are you getting such mileage?
I get over 40 mpg easily anytime on any longer trip without stops. But I can get anywhere near 65 mpg only when going downhill.

I keep track of my gas purchases and fuel economy in a spreadsheet every time I buy gas. I use the “B” trip meter to track each tank of gas and the “A” trip meter to track over thousands of miles.

My “A” tracking has shown the Civic’s gas mileage meter to be accurate to within 1-2% over the past four years.

On long 72mph freeway trips, I get ~41mpg, which is what this chart shows. On a 300 mile “blue highway” trip through Georgia, I got 51mpg. This with plenty of small town traffic lights and stretch stops every hour. The chart shows ~56mpg at 56mph, which sounds about right.

For mpg at 35mph, I’m going off the Civic’s mpg meter, which I have confidence in, based on my fuel tracking.