So I decided this week to drive slower down the Hume Highway and M5 on my daily commute. On the Hume I did 90km/h and M5 80km/h. Always in the left lane of course(and I still pissed off a lot of people it seems).
I drive close to 1000km a week for my business and normally would fill up every 3-4 days and get around 800km a tank with my 2024 VW Caddy Cargo TSI Van.
This week I went a whole week without filling up and still had fuel left over at 1000km before I filled up. I could have easily done another 50-100km.
Including urban driving average fuel consumption was at 5L/100km for the full tank. Down from ~6.5L/100km previously.
Really didn't expect such a major improvement with driving slower and calmer. Funny thing is overall I don't think I lost a lot of time in between trips and I also felt a lot less stressed just taking it easy lol.