It depends SO much on the route and speeds.
... Hills (and the type of hills) can also help or hurt,
... and truck traffic can help too.
... I do think driver attitude and state of mind makes a difference.
Bingo! Experience has and continues to show me that red1dr is about as right as you can get regarding getting the maximum MPG from your Insight on any given run.
The Summer before, when I first had the "Silver Bullet" I was able to get 97.1 MPG on a 24 mile run and a week or two later I got something like 97.9 on the identical run; have yet to "crack" 100 MPG and if I'm going to do it, it will be on that run - and it'll be in the Summer when I do it. This Summer on the same 24 mile run I was able to get 92.1 and the following day if I recall correctly I got 92.4 on a repeat run. Note that all four runs were in the Summer, NOT Winter. When Winter comes expect your MPG to plumit.
On a run North of here, another twenty some mile run, initially I was disappointed with the fourty and fifty MPG results but by paying attention to the roads, where I could coast, I did, where I could go a lot slower (forty and fifty MPH as opposed to sixty MPH) I did and using that experience, now I routinely end those runs in the low to mid-seventy (70-74) MPG range.
You might also note that the "Silver Bullet" is a CVT and if your Insight has a manual transmission, there is no doubt what-so-ever on this end that in the Summer were you to run the same roads I'm running, odds are it wouldn't be very difficult for you to be registering 100 MPG or better at the end of those runs - again this would be in the Summer, not Winter.
If you're a new Insight owner/user it is reasonable of you to expect that it will take you several months to really begin to get the best MPG out of that little car for the roads you travel most, and are most familiar with.
Hope this helps some.
Fred / Proud owner of "The Silver Bullet"