Hi Julia, welcome to the NICO Juke forum. So glad to have you on board.
I can't give you any advice from personal experience, but I can lead to some good information.
Here is a discussion on fuel from one of our users... looks like he is getting 29mpg pretty regularly now that it's broken in.
my-mpg-after-1500-miles-t515451.html
My understanding on the fuel issue is that premium is recommended, but not required. Though I suspect the milage on lower grade fuels would be less and not justify it.
Let's do the math on that.. If you drive 200 miles per day, that would be 6.9 gallons per day (at 29 mpg). 6.9 gallons x .30 per gallon premium = $2.07 per day or $62 per month.
For most people we find that the cost of premium fuel winds up being much less per month than they expect. But, you are not "most people".. driving 1400 miles a week or over 72,000 miles per year is TON.
Clearly your priority list needs to have fuel efficiency at the top. The question is.. how important are those other things that the Juke might provide? Fun, sporty, comfortable, stylish, safe, awd, suv ride height, space, etc...