Not sure either, 120 BHP, I filled up a little while ago and got 26MPG out of it, but that's with the cold weahter, and realized that my tires were not inflated to the correct bar when fully loaded. So hopefully in spring summer time it should be as good as my old Berlingo.
500l should do okay, but if you need to do dirty commercials for most of the day, even 650 won't be enough for that.