Going too slow is definitely inefficient for non-hybrid cars and trucks, but the optimal speed for most vehicles is certainly not higher than 55 MPH. Average f

Going too slow is definitely inefficient for non-hybrid cars and trucks, but the optimal speed for most vehicles is certainly not higher than 55 MPH. Average fuel economy for cars and light trucks decreases 12% going from 50 to 60 MPH: https://www.energy.gov/eere/vehicles/fact-982-june-19-2017-slow-down-save-fuel-fuel-economy-decreases-about-14-when https://www.energy.gov/eere/vehicles/fact-982-june-19-2017-s... Heavy trucks are the exception, they are typically designed for an operating point of 65 MPH. However, there are huge losses above that speed. No reason for a heavy truck to be going 70 or 75 MPH. The American Trucking Association actually endorses a nation 65 MPH speed limit for trucks, which they say would save 280 million gallons of diesel per year: https://www.fleetowner.com/emissions-efficiency/article/21660208/fuel-economy-101 https://www.fleetowner.com/emissions-efficiency/article/2166...