The Senate is currently debating a bill:

link to article

Do you think this is a Good Thing (tm) for the government to do? 

Yes, of cause the Government should mandate higher MPG standards following massive failure from the Auto Maker especially the former big three GM Ford and DC, it is high time we Americans start to appreciate the merits of high fuel efficiency in the name of being smart and economical. It makes sense except to the folks in oil business who would want us to consume more gasoline. 

interesting thought.

should the government mandate that vehicles meet MPG regulations? or should the government tax gasoline so that we will want to buy more fuel-efficient cars, and let the market determine the solution? 

I am for letting the market decide. Consumers are the ultimate decision makers.

When we get gas over $5.00 a gallon, people will start demanding better fuel efficiency, and the auto makers will comply. 

When we get gas over $5.00 a gallon, people will start demanding better fuel efficiency, and the auto makers will comply.

when gas gets over $4.00, i'll drive less. carpool more. investigate alternative energy sources.

i'm all for letting the market encourage automakers to change.

the question is, should government accelerate that process by imposing additional new taxes? 

I am not sure how imposing new taxes will help the consumer.

If the taxes are levied against the car company's for not complying with a new mpg law, then the consumer will end up paying for those taxes when the prices of cars go up.

A tax against any corporation will always be paid by charging the consumer higher prices.

Higher taxes will not accelerate any process. They will only accelerate higher prices. 

Higher taxes will not accelerate any process. They will only accelerate higher prices.

True. But the higher prices may accelerate changes in human behavior. Is that a worthy goal? 

Higher prices in what? Gas? Cars?

Higher prices in anything can change human behavior in the short term, but as those price changes become 'normal', human behavior will return to normal as well. 

Better MPG would probably help the American makers sell more cars and be more competitive against companies like Toyota that are steadily taking more and more of their market share.
Why they are not doing it on their own I have no idea. Seems like a gimmie. 

There are a lot of people that cannot afford new cars, so taxing the gas would only hurt them.
Require better mpg from the manufacturers, then wait a few years for some of the older cars to go away and mass transit to improve, then look into taxes.