MPG city vs freeway

The speed limit on the highways around here is 80 MPH for the interstate highways and 70 MPH for the two-lane state highways. My wife teaches at a rural school about 50 miles away from here, so she drives the 2019 Prime. 20 miles of that is on the interstate, 25 is on the state highway, and 5 miles of that is around town.

Wind resistance at the highway speeds is proportional to the speed squared. There's a sweet spot for speed, below which you're not putting on the miles to get the best miles per gallon. There's also a point where gonig faster takes more power to push the car through the air so you don't get the optimal miles per gallon. Also, on the highway I don't get any benefit from the hybrid. Around town, I can cycle the energy from braking to the next acceleration. On the highway, at least with the relatively little traffic around here, we don't really stepon the brakes that much.

Also, there's the impact from the plugin, since I have a Prime. We can actually use the EV, but for only 20-25 miles per day though. The highway sucks that down much faster than around town.

That being said, we get around 70 MPG (treating the EV miles as free miles) because of the highway speeds.

 

This, coupled with "stop and go", is never going to yield good mpg. If on the other hand you were tooling around town all day, like a cab, I think you'd see stellar mpg, calculated from fill-ups and distance travelled.

 

Short journeys will result in low fuel efficiency as th engine spends much of the time arming up to optimum temperature. If all your short journeys are like that it would explain your poor mileage under city conditions.

My commute fuel consumption is mainly for journeys that are 30-40 minutes in duration.

The EPA figures are with the engine hot.

kw