The 4 speed autos I've driven while caring about fuel economy usually shifted to the final gear around 45mph. The 50mph you are seeing could be normal, but probably can be improved upon. It was the manual Echo you drove before this one? Better fuel economy will be see out of a step (traditional) automatic with a driving style than you would use for fuel economy on a standard.
With a standard, you accelerate slowly; keeping revs low while shifting early. With a step auto more aggressive acceleration can yield better overall results. It's because the step auto is moving the car by pushing fluid through the torque converter. That is where most of the inefficiency of the auto lie.
So you want to get to the top gear possible for your target speed to get out of that wasteful thrashing, and the transmission might also upshift at a lower speed to a more efficient ratio. Letting up a bit on the accelerator may also get the tranny to upshift. So the 50mph shift point you are seeing may drop down some. Once cruising near a steady speed, the torque converter could lock up. Then the engine power isn't sloshing through fluid, but a direct, mechanical connection in the transmission.
Most current transmissions can lock up the torque converter in nearly every gear. Toyota is a, um, 'conservative' car company however. The Corolla didn't get better than a 4 speed until the newest model, and the 4 is still on the base trim, plus the Yaris and most of the Scions. Which is likely the same or close to the 4 in the 2004 Echo. A 3 speed was base in the Corolla into the '90s.
Without knowing anything about your daily drive, 30mpg is on par with the EPA ratings of the car. It should improve as your driving style shifts from manual to automatic driving, and as the weather improves(tire pressure could be low at this time), assuming the 2003 is a recent acquisition. Toyota's cheapness in automatic transmission selection for smaller cars, and the better control of the manual, will likely mean you won't reach the fuel economy of your older Echo.
http://www.fueleconomy.gov/feg/Find....15847&id=18606
But we still need to address the vibration issue. For that we need more info. How many miles are on the car, and is all the required maintenance up to date, and fluids at the correct level? If it was missed, a tune up might fix the vibration with new spark plugs and wires. Start with the basics first.
Checking if the vibration goes away while in neutral is a good simple test. Is it actually only while you are stopped? A noise or vibration could lessen or simply become less noticable with the car in motion, but still be there. Does the car being cold or warmed up make any change to it?
Linear Mode
