Odd mileage....

[shinlee]

I've owned my yaris for over 3 years now, and have always consistently gotten between 32-36mpg city mileage, but tonight I went to fill up and went to check my mileage (per fill up ritual, keeps me knowing why I own a yaris, lol) and I got 42.92 mpg! WTH?
Same drive to work and back, and now since it's starting to get a little bit warmer, I even used the AC the last 2 days. Car has 44K miles on it, well beyond the fable'd "break in" period, so the only thing I can think of that I've done recently is throwing in a bottle of Lucas fuel injector cleaner on a full tank of premium instead of my normal regular.

It's been about 15k miles since the last bottle went in, and I don't remember this result, but has anyone else experienced such a drastic mileage jump? 7mpg's is a hell of a lot from one tank to the next on the same exact drive.