Looking at purchasing a used Prius and I have some questions.

The previous owner of my car was pretty tall and he installed seat rail extenders on the Prius. That can help you out with the height issue.

I would expect between 37 to 42 MPG. Prius gives great mileage in stop and go traffic (between 45 to 50 MPG) but not on the highway. I drove from Las Vegas to Houston this December and that was close to what I was getting. Except for the places where I was going downhill.

I don't know why this would be the happen. Usually Prius is my area do not stay on the lot too long. When gas prices are up they go fast. Could be your area though.

 

When I drive my 2008 touring on the highway I average about 46-47 MPG. The reason I'd choose on for mostly highway driving is the reliability more so than the mileage. The second generation Prius is by far the most reliable car on the road when you look at the statistics. Naturally there will be a few that don't fit that description, but the vast majority do. Compare the actual ownership repair experiences of those with the newer diesels to those with the gen 2 Prius, add in the price difference of the fuels and the choice, in my opinion anyway, becomes obvious.