Fuel Grade is a debatable topic for the Cruze. I've been using midgrade (89) whenever I fill up. I've noticed more consistent mileage and slightly better mileage as well.
Upon further investigating the Cruze's 1.4L ECOTEC Engine, I finally found the engine specs (link below), and noticed a compression ratio of 9.5:1. Now knowing that, I'm glad I put in midgrade at least, especially since it is a turbo car.
Cars that require premium fuel usually have a compression ratio over, 10, ours being at 9.5 I think warrants a minimum of midgrade for better operation. But I'm not a Engines Engineer, and I know the Cruze has knock sensors that allow it to use 87 octane, but I'm sticking with midgrade or higher.