Toyota's with 1NZ-FE engines have TSB re: poor gas mileage & injector clogging!
If you own a Scion xA, xB (1st gen), etc. with this engine, Toyota has a TSB (technical service bulletin) out for it. The fuel injectors clog easily, and when so, will result in poor gas mileage.
eg My xA only got 26-28mpg forever, then with 60k service and injector cleaning, now get 31+. Sadly, this means use of top tier gas, techron fuel additive, and monitoring of mpg to watch for an injector clogging.
tsb = it won't kill you, but the car maker messed up and sold you a car with a problem.
eg. Very angry at Toyota for not telling me about their xA AC not cold enough tsb! Too late to get the $1300 compressor and parts replaced free, but no wonder mom's Tercel has much colder ac! Now, every hot summer is a suffering drive!