I replaced my stock 15" Yokohoma tires (30k miles) and put on stock 15" Michelin Assurance FuelMax. I've driven a little over 100 miles on the new tires and I am at 33MPG average. This coming from 49.6MPG, which was comprised of a 6k mile journey across the US (plus local driving after we moved to CA) with 2 passengers and 6 large suitcases. Something doesn't seem right. Nothing else has changed with the car. New tires were put on 3 days ago. I read others saying a break-in period, but that was factoring a 5MPG loss or so. How am I down almost 17MPG?