Hi Folks, We just got back from a long, high speed college open house trip from NJ through VA and back, putting about 1200 miles on the Prius in a few days. I wanted to share some observations regarding the gas mileage versus Interstate speed traveled that I saw for the purpose of any conversation that might ensue, or for those who wonder how a Prius behaves. I will talk a bit about handling and engine sound too.
Disclaimer: My numbers are from observing the 'MPG Game' on the screen, not from fill-up data, as my speeds necessarily fluctuated, but I was able to hold them for a few 'bars' at a time. [I generally find that the actual mileage is maybe 2 MPG lower for a tankful than is calculated by the computer on the screen.] This data is just meant to be relative at different speeds. This trip also primarily used 'NormalFoot' instead of my trained 'PriusFoot' - by this I mean that I drove to get there as quickly as possible based upon traffic and road and police conditions. I did very little foot feathering to purposely try to get the Prius to go into electric mode. I just drove it. Therefore, even at 'around town' speeds I was getting worse mileage than I usually get around here using my PriusFoot.
At around a sustained 65 MPH we were getting about 52-53 MPG on average. At around 75 MPH this dropped to about 47 or so. At around 80-85 the mileage was down to the 42 range.
The Prius handled surprisingly well at 85 MPH until the crosswinds perked up following the cold front. In no winds 85 MPH was rather stable and still rather nimble (I appreciated when the road cut through a forest that shielded it from wind). When the winds manifested themselves I did not go all that much over 80, as it seemed just a bit squirrelly. At these high speeds it did have enough power reserve to get out of its own way when needed. Seat-wise, I never got uncomfortable in all of those hours of driving it, which also surprised me a bit.
One surprise was the sound coming from the engine up at those speeds when I needed to put the foot down. For the first couple of times I was looking over my shoulder for that motorcycle passing me on the right. That's what I thought it was until I figured out that it was my own car [grin]. Not a loud sound, just one I had not encountered prior to this trip. I have been PriusFooting it up to this time and this was a new thing.
Otherwise it behaved quite well carrying 4 people and their stuff. I can live with this thing for a few hundred thousand miles... Tomes