I don't idle at all but I do sometimes sit in traffic and will just ....roll. I've since used another tank and I have notice my mileage increasing so I'm hoping it is just the break in period. Maybe I'm driving the car too gently and the car is just asking to me drive already!
Seems like around 18-19 mpg is what most are getting. I've slowly climbed up to 15 now. Another tank or 2 and I should be with the rest of you! Probably nothing wrong with the car then.