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I decided to see what difference low rolling resistance tires make versus higher rolling resistance tires in steady state highway driving. We all know they make a difference in city and lower speed driving. But what about highway speeds when aerodynamics matter?

I decided to do a test and actually see if tires make a diff on the highway since it doesn’t seem like there are ANY tests done on YouTube or other forums or any tire companies?!?

I chose a dry day with no wind. Ambient temps of about 42 degrees and sunny.

The test road is about 8 miles going west on highway 26 and 8 miles coming back east and completely flat

My high grip tires were the Bridgestone blizzak winter/snow tires inflated to 38 psi

The more miles I drive, the more stable my mpg average since my ioniqs hybrid system alternates between engine and battery then averages those together. There is no instant mpg like Toyota hybrids.

Going west from one marker to another, I averaged 58.5 mpg and then looping back the TOTAL mpg for the trip with the extra miles was 54.2 mpg

I then went to Costco, dropped my car off and got my winter tires taken off and my all season eco tires put on. Process took less than an hour

My low rolling resistance tires are the Bridgestone ecopias. Inflated them to 38 psi also

I went out and did the exact same stretch

Going west I averaged 59.5 mpg. I was scratching my head thinking “ seriously only a 1 mpg jump? Doesn’t seem worth the tire change… let’s continue and see what the average does with more miles”

Then going east and back to the check point, the TOTAL mile average was 62.5!

What was funny is even though the two first half of the trip averages were almost the same, doubling the miles, the winter tires averaged down for mpg and the lrr tires averaged up

Also a side note, the winter tires had thinner treads and about 40,000 miles on them and I had to throw them away today. They were over 2 years old

The ecopias were purchased new less than a year ago and have a deeper tread. So the gap between the tires fuel economy probably would’ve been even bigger if they were both new tires with the same wear

I’m now over inflating the ecopias to 41 psi and will probably add my wheel skirts back on next week.

Also the tests were done at 65 mph with cruise control set. Maybe the rolling resistance difference closes tighter at higher speeds like 80-90 mph when aero pretty much takes over completely.

Either way, my steady state highway test results show that low rolling resistance tires make a difference even at highway speeds for the average driver!