Driving the Insight for mileage is quite different from driving a normal car. I was getting upper 50s in my Civic rated for 30 MPG (autotragic, so no 80 MPG like yours
), but my first Insight tank was only 66 MPG.
P&G doesn't work, DWL at 30-40 MPG in 5th works best, lean burn all the time. Lean burn kicks out when you go below 30 MPH in 5th and 25 MPH in 4th.
Air the tires up, skirts help some, underbody panels, tire pressure, check brake drag, spark plugs, all the normal things. Wrong tires will cost 5-20 MPG depending on brand and size. Mirror delete = +3% FE. Full lower grille block has coolant at 202-207 *F at 90 degrees outside and 197-202 *F during the winter.
The Insight with a working IMA has a slight constant background charge that will rob MPG. It only stops when your battery is at 18 bars or higher, at leas that's what it was on my '06. That charge never showed up on my Insight, but whenever an acceleration brought my battery down to 3/4 bars lit up on the display, it would background charge slightly (no visible charging) and make me lose ~10 MPG until the battery was full, thus negating most of the fuel savings from electric acceleration.
IMO, for ultimate MPG in the hands of a hypermiler, you need the battery deleted (weight savings outweigh battery benefit) or an IMAC&C + OBDIIC&C to manually control the battery. Without IMAC&C + OBDIIC&C, all the battery does is make the car faster, provide autostop and silent start, and capture energy for people who actually use their brakes, but at the expense of background charging and an extra 100lbs in the back of the car.
Working AC will cost you big in FE, as it does in any small econobox.