I kept track of mpg using the gallons and miles method early on its life, but then, after learning about the bladder, gave up. The car's values were close enough, but when good old fickle WI winter weather hit, it became impossible. I could fill up when it was 0F and then the next time I needed a fill up it would be 40F. So, I've just come to rely on its reported mileage. Probably wrong, but it is all relative.

Best mileage? Oh, I think it is worse than you have (or is what you mean)....stop and go freeway traffic. If I screw up my departure from work and end up in freeway rush hour, I can easily exceed 70mpg on that segment. Unlike urban driving, you don't have any rough accelerations--just gentle up to speed (if it is <34mph then it is all electric) and coasting to recoup the battery. I've gone 20 minutes on electric.

Thankfully, I only hit that situation once a month or so. Hard to think they built such an interesting piece of engineering for a situation you shouldn't be in in the first place.