BETTER fuel economy at recommended tire pressures

[Bluebaby]

I got an '07 3-door manual a few months ago, my first car of my own. The clearcoat's fucked but I don't love her any less because of it.

Since then I've been running between 36-38 psi because that'll get me better fuel economy right? At between 6.5-6.9L/100km between fillups (I normally fill about 400km into a tank), I was pretty happy.

Wrong. 2 fillups ago I lowered my 2 month old 175/65/14 Hankook Kinergy ST's to the doorjam-recommended 32psi, curious about how much more fuel I'd use. To my shock, over the first 400km I got 6.0L/100km on the dot. I was skeptical, thinking the pump I'd used for that fillup cut off earlier than other ones. But today I went back to the same pump after 350km of driving and recorded 6.1L/100km. No changes in driving style, weight of the car, other maintenance, nothing. Only the tire pressure changed.

Might go lower them to 28 and see if I get 5.5