[AfAX]

A Q3 has a 64 liter gas tank (specifications). I have driven a couple of times till I only have 10 kilometers left (computer). When I fill up the gas tank, I can only fill 60 liters, with 1 liter or less left in the tank this only makes 61 liter instead of 64l. Is this normal?

 

[rontheman]

I think there are 2 reasons for this:1 The entire tank contents are not available for use. Most fuel tanks (cars, aircraft, ships, fuel oil etc) cannot drain out entirely (maybe to avoid airlocks in the fuel lines) and so there is always some left in the tank that is unusable.2 There is a further usable reserve in the tank once the computer range hits zero. On other Audis I have owned, I have driven the car up to 5 miles after the computer recorded a zero range (I know it's stupid! It would be interesting just to see how far the car would travel after a zero range was shown, but that would entail draining the fuel lines, which I think can cause damage to the catalytic converter, or something like that, as well as introducing airlocks into the fuel lines. I suspect that there is about a 10 mile reserve, or about 1 litre.Of course, there is an argument that the specified fuel capacity should be the usable volume, rather than the nominal volume, but that will never happen (think computer disc drives where a nominal 100Gb drive actually only has, say 95Gb usable). Also, the nominal capacity is a known quantity (i.e the volume of the tank), whereas the volume of fuel can expand/vary with temperature and pressure. Finally, when filling the tank, do you stop filling when the pump handle trips, or do you trickle feed to the point where you can see fuel in the filler neck?

 

[AfAX]

Finally, when filling the tank, do you stop filling when the pump handle trips, or do you trickle feed to the point where you can see fuel in the filler neck?

Well this is a little diffent from my previous A4. When it stopped filling, I could still add at least a liter in the neck of the A4. But in the Q3, full seems full and I can only add a tiny little bit.In your answer, the airlock makes sense.Further, I think when you hit 0 on the computer that you still have 10 kilometers (or miles) you can drive, since the computer in Audi goes in steps of 10. Wouldn't be right that it says you can drive 10 kilometers, and 20 meters further it says 0 kiliometer ;-).And maybe?, 10 kilometers after it hits 0, there might bealso some reserve, so you are a little further away from draining the fuel lines, but I'm not gonna try it

 

[rontheman]

I wouldn't assume that the reserve fuel equates to exactly 10 or 20 kilometres. I think one should assume there is a "bit more" available, might be 5 km, might be 10 or 15km. It isn't an exact science at that stage.Also, from our other Audi (also an A4), I once found that if the computer showed zero, and I added just 5 litres (the nearest garage being very expensive!!), the computer still showed 0, even though I knew I had added sufficient fuel for at least 60km. The computer only showed an expected range once a significant (>5 litres?) volume of fuel had been added.

 

[AfAX]

Had the same issue with the previous car the day the Q3 arrived

. The computer was at 20 km, so I added 2 liters to be sure to be able to drive the 30 km to the garagist and give him the car with 20km left on the computer (he gives me a tank that is nearly empty with the new car, so that is what he gets ;-) ). But then 10km furtherthe computersuddenly went down to10 km. I was very surprised and stopped at thefuel station there, added another 2 liters, but it still gave 10km.I didn't want to givethe carwith a 'complete empty' tank (still only 10km on the computer) and filled it up a third time with 1-2 more liter at the gas station near the Audi garage... and it still gave 10km on the computer. I tankedover 5liter for 30 km so schould have nearly 100km (instead of 10) on the computer at the end.Strange behavior indeed.