The Simple answer: Radial Tires Roll down the road easier.
How and Why is quite complicated
definatley.
I'm assuming that you are asking about fuel mileage. Reduced fuel mileage is mostly caused by under inflated tires. 32 psi for the Toyota Echo tires is required. Don't buy fuel boosters or fuel cleaners because they don't work.
Compared to previous versions of tires, radial tires have less rolling friction or less friction with the road while in motion. The result of this is that the tires are generally quieter when driving on the road than the previous version and also allow for better fuel economy.
There are some practical ways to increase the gas mileage but you can use also Fuel Infusion what is a powerful fuel catalyst. Fuel Catalyst realy helps to increase to boost your engine power and your gas mileage.
There is no fuel additive that will increase mileage. This is a myth. None of the snake oil additives work.
One way would be to install a tuner, but there are other ways such as exhaust, intake, tires, driving habits, etc.
How it rides, handles, fuel mileage and power are affected.
No, your speedometer will be off and power and fuel mileage will be adversely effected.
To increase fuel mileage.
It could make it better, but nost likely make it worse.
There are a few ways to increase gas mileage but the most effective is the use of fuel infusion. Fuel Infusion is a powerful fuel catalyst that improves the efficiency of the combustion process in your car's engine.
You can increase fuel mileage by installing a tuner or a bigger exhaust. I'm sure there are some other ways also if you look into it but these are two of the best ways.