I wonder whether you guys experience this before....
I got my IS250 for about half year. Most of the time, It run about 18 miles per gallon in city and 27 miles per gallon on highway.
Recently, I have travel somewhere else with it and I was able to squeeze out 30.5 miles per gallon on the highway (average speed around 75)
I got back home now, and It run more miles per gallon in city these days.
Make any sense?