Part of my i30 buy decision was the based on fuel consumption. The largest set of stats that I could find on the internet was at spritmonitor.de.
It is a german based web site but with lots of other foreigners participating. Click on the british Union Jack flag at the top right of the logon screen to switch the language to English.
Current Hyundai i30 data includes....
203 diesel i30s avg. 5.82 L100K
278 gasoline i30s avg. 7.49 L100K.
You can drill down to review each owner’s list of refuels, with related driving conditions, etc.
I subsequently now use the website for my own new i30’s stats. I particularly find the mobile URL <m.spritmonitor.de> works great on my iPhone - I enter the refueling data before leaving the gas station – no more spreadsheets or apps necessary.