Mostly Greece does not have self service stations so it is not a question of laziness. |
I usually get out of the car and stand next to the person filling up as a matter of habit but I would certainly do it if I thought I couldn't trust them. I think I would go further and get out of the car without releasing the filler. I would then point to the expensive pipe and forcibly say "ΟΧΙ", point to the standard unleaded pipe and forcibly say "ΜΟΝΟ ΑΥΤΟ" and then release the filler.
More probably I simply wouldn't use that garage.
PS For those in the Chania area with diesel vehicles I am told that the fuel station outside Carrefour near Mournies is the safest one to use. I am told that the taxi drivers clubbed together to get a filter fitted so there is guaranteed no water in the diesel.