Hello, Having had a 2007 A6Avant from new until, at 203k, it gave up last summer, now I have a 2nd hand 2017 model and am getting to grips with how much more of a ‘snowflake’ this one is. Anyway, simple question: should all fuel flaps lock? Have discovered that my flap doesn’t lock so, with the cap itself not locking either that’s an obvious weakness. 
Thanks! 

Hi Louise.

I think all fuel caps should lock by law some way or another. In all the years I have had my Avant I have never tried to open it other than at a fuel station. I am going to have to try now. Will get back to you.

Tony

hi louise, i know i have a different audi to yours, but is yours a push in and out button like mine.(see pictures)if yes,do you have any wd40 or similar spray,and spray the part were i have circled it(pic 1) and keep pushing the button in and out while occasionaly spraying it.,and it may eventually come out. (pic 2 showing button in/locked).regards stephen

Thank you Tony and Stephen; I shall have a look at this. Appreciate your input; thanks very much. Louise 

Hi Louise. Had a look at my Avant. Stephen is quite right as you close the lid, the plunger spirals in locking the flap. Perhaps as he has said it may be stuck in the down position.

Tony

Thanks to those who read or replied to my fuel flap query; there was a duff sensor which has now been replaced. 

They can be bought for as little as £10 if faulty, don’t know the quality (I had an issue with mine recently, different issue but found it had got confused with itself followoing a flat battery - cleared codes and all ok)