So when I first got the car I was getting about 550-600km/tank and I thought that was average (I use to get that on my 24v VR6 Jetta). Then I started driving it like a grandma. Smooth slow accelerations from green lights, shifting at around 2k RPM (except when merging onto the highway) and was averaging about 680km-750km.

Then I decided to fill my tank passed the point where the gas pump stops/clicks and I can't remember how many extra liters I put it into it. I'm guessing maybe 5-7 extra litres.

I filled up last Friday and have driven lots of highway as well as city and still haven't filled up. I think I could probably squeeze it to about 870-900km but just in case theres somerthing wrong with my fuel gauge I don't want to risk being stranded.

My car is completely stock and I have my winter tires on still.

 

First of all, the gas pump stops for a reason. If you do not leave room for vapor pressure, you risk serious damage to the fuel pump and tank, not to mention the charcoal can that has to handle it, as an end result.

830.9Km = 516 miles / 13.2Gal = 39mpg, which is at the outer limit for efficiency.

Excessive fuel economy can cause serious overheating of engine components including the pistons, valves, and catalytic converter resulting in early failure of these parts.

In total, excessive fuel economy constitutes a problem that needs to be dealt with, and do not over-fuel the tank in your car.