yes ive searched for a thread on it, but i cant seem to find much tbh

i filled up last night, at the time the fuel light was on and the computer was showing 60 miles left, and i managed to get in 39L

can someone tell me, or even better show me with some pics, how your getting 50+ litres into a tank that is listed as only taking 45L

ive read threads about a nipple/button which releases air from the tank ?

There's a reserve of 7 litres which can be 'got at' by pushing the filler nozzle to the front of the car whilst filling up (there is a button / npple to the right - as you're stood at the tank filling up). Usually you have to lever the nozzle pretty firmly (push hard) to keep it in place as it tries to spring back. You'll hear some hissing.

60 miles left is going to be a good 7 or 8 litres for starters, so there's your discrepancy for starters! As for the button / nipple, I thought it vented the expansion tank, and you just added more fuel after all the air's escaped. It certainly SEEMS to have worked like that for me when I've tried it, although if it's true, you've lost your expansion space, so shouldn't do it unless you're going to drive a decent distance (to use some of the fuel) before you park the car for any length of time...

search for "ventectomy"

http://briskoda.net/fabia-i/ventectomy-summer-safety-fuel-filler-thingie/57173/?highlight=ventectomy

There's a common Myth about 'overfilling' being an issue where fuel expansion is concerned.

Diesel and Petrol have different characteristics, one of which being the temp that they give off vapour/evaporate.

From memory, petrol gives off vapour at -21c where as Diesel gives off vapour at +54c, so expansion isn't really an issue in this country (with deisel), even in the peak of summer.

In fact, filling to the brim is better for the car, as it reduces the space for condensation, meaning you are less likely to get water in the bottom of your fuel tank.

Is it not the expansion of the liquid itself due to changes in temperatures? Although I admit the change in volume of 45 litres of fuel can't be all that much from one day to the next... :ne_nau:

The difference in volume in a small amount is barely noticable.

You only need to worry about the difference when dealing with large quantitys.

In HOT places like afghan, i could dip a tank on one day when the temp was 40c degrees and it would be showing 2-3000 litres a day later when the temp was nearer 50c degrees.

That was aviation fuel, which is almost identical to diesel, but without the lubricity as jet engines don't require it.