Cruise Control at 65mph

Last weekend I went to Seattle, and on the way back had the patience to drive for an entire tank of gas at 65mph. Often on a long drive I’ll have the cruise control set approximately five to ten over the posted speed limit. This time I left the cruise control speed at 65 even after I got to Idaho where the posted speed is 80mph.

A very interesting thing during the drive from Portland to Boise, the trip computer was regularly calculating the range at a number that, when added to the miles already driven, calculated over 600 miles in the tank. The pictures above are showing an estimate of 580 miles in the tank after having already driven 400 miles.

A quick calculation of driving 432 miles at 65mph vs the same distance at 75mph tells me that the faster speed only saves me 53 minutes. This time I arrived home with over a quarter tank of fuel. Previous times I’ve had the low fuel warning light on when I was still 20 miles short of reaching home. If you figure I could have put another 7 gallons of gas in the car at over $2.50 a gallon, I saved about $17.50 for that 53 minutes. It was on a day that I hadn’t planned on doing anything beyond driving point to point, so I think it was worth it. Just the difference in gas price between Idaho and Washington pushed that difference in cost to over $20.

The real calculations below show that I only achieved 22.72 mpg during this stretch, while the computer was displaying 25.0 mpg. The 16.59 in the next column is the average mpg over the entire lifetime of my vehicle.

3/29/2017 11.555  $    29.45 138615 17.40 16.56  $      2.55 201.0 4 50
3/31/2017 21.918  $    63.98 139002 17.66 16.57  $      2.92 387.0 2 194
4/2/2017 21.265  $    61.01 139401 18.76 16.57  $      2.87 399.0 2 200
4/2/2017 5.196  $    14.23 139513 21.56 16.58  $      2.74 112.0 0 112
4/3/2017 19.011  $    48.08 139945 22.72 16.59  $      2.53 432.0 1 432
Oregon I84

Oregon I84

Oregon I84

Oregon I84

Sometime I may have the patience to try driving the stretch at 55mph, which was the law when I was back in university and drove a car that regularly achieved 38mpg. Views like these last pictures are part of what makes the drive itself worthwhile.


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