Is it true that higher octane gasoline is consumed more slowly by engines,and it doesn't pay to purchase regular gasoline solely to save $$ when it is not required for your vehicle?

No it is not true that premium gas burns slower than reg. It is a complete waste of money to use a higher grade than required by the manufacturer.

macric is correct: premium gasoline has no advantages for ordinary cars. if you have a high performance car which required high octane fuel, then it's a different story. but for most cars and light trucks, you do not get better mileage, better emissions, or better anything. all you do is waste money.

There may be a slight semantic misunderstanding. Higher octane gas does not improve gas mileage per gallon as macric and and sam confirm. It does actually burn slightly slower in the cylinder to avoid the 'knock' that occurs if low octane gas burns (explodes) too quickly in a high compression engine like in a race car. It does not burn slower as in going more miles. There is no benefit in a normal car.