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2005 Chevrolet Avalanche - MPG

My Q is about what Tom said in Car Talk 04/04/2014 “They (Bridgestone) found that for every mph you increase over 55, you lose an avg. of 1.6 mpg.”
Really? So, at 75 mph - 20 mph faster - you lose 20×1.6 = 32 mpg?

Mpg loss from speed is not linear. 1.6 mpg for every 1 mph is an incorrect generalization.

Tom is deceased, Ray doesn’t post here, and the show has been in reruns for a decade.

My Avalanche loses about 2 mpg per 10 miles and hour. My Mustang loses about 0.75 per 10 mph. Losses depend on frontal area, coefficient of drag and speed squared.

Those old calculations about MPG loss vs increasing speed were awesome until cars starting coming with real time MPG meters and folks realized that at a steady 75 MPH they were crazy efficient.

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My 2012 Camry with an EPA rating of 35 MPG and less efficient but better riding and handling tires with double the treadlife still gets 33 MPG on real world trips at cruise control max speeds of 75 mph. this is a 730 mile trip with 2 border crossings and about 175 miles of two lane roads through towns. The mileage is calculated by odometer miles and gallons to fill.

My Corolla loses 7 or 8% of its mpg going from 60 to 70mph. I’d assume something similar for other vehicles. As others have said, it’s not necessarily linear.

That seems quite a bit more than I’d expect for mpg loss vs speed. Maybe there was a typo or somebody mis-spoke. I’d expect something more like this

55 mph 35 mpg
65 mph 32 mpg
75 mph 27 mpg

What is your mileage now with your 2005 avalanche at 55mph?

maybe 1.6%

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I have a 2009 Challenger with the 5.7L V8.

When I’m on a road trip with it, the car gets around 24 MPG if I keep the speed at 70 MPH.

If I do 80 MPH, the fuel economy drops to maybe 22-23.

It it enough to worry about? No. Now if the fuel economy dropped to below 20 all of a sudden, that would get my attention. But aside from that, I have other things to worry about.

Just my 2 cents.

It’s incredible how steep the mileage loss is on pickups/SUVs. That wind resistance is a bear…

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A hungry bear!