Looking over my previous data for the trips, I had one trip with 29.7 MPG (7.92L/100km) total (that includes going to the ski slope and back) and I remember now that it was with a lower grille block installed.
From what I remember it did not show much improvement over the warm-up times so I did not use it later on. But looking back at mpg data, it did help. Another thing to test.
The grille inserts to block the upper grille are cut and ready for testing.
So far on the list to test:
Front tire deflectors
Rear tire deflectors
Gas tank to rear bumper transition
Lower grille block
Upper grille block
Some sort of rear spoiler (inspired from here:
https://ecomodder.com/forum/showthre...mph-13476.html)