Can I use the toilet?
'Bagno' — 'BA-nyo'. Two syllables; 'gn' is a nasal palatal sound, like 'ny' in 'canyon'.
Ask at the counter when you need to use the toilet, especially at smaller stations where it may be locked and you need a key.
'Posso usare' means 'can I use'. 'Il bagno' means the bathroom/toilet. At many Italian petrol stations, especially small ones, the toilet is kept locked and you must ask for the key at the counter.
Dov'è il bagno?
Where is the toilet?
Simpler direction question when the station is large.
Ha la chiave del bagno?
Do you have the key to the toilet?
Directly asks for the key when it is clearly locked.
C'è un bagno qui?
Is there a toilet here?
Checks for existence before asking where it is.
Toilet quality at Italian petrol stations varies enormously. Motorway 'Autogrill' stations generally have clean, well-maintained facilities. Smaller roadside stations may charge €0.50 in the form of a coin-operated door or a token from the counter.