Do consumers need laws to make automobile companies increase MPG?

This article in CNN claims that one reason for the government to require automobile manufacturers to produce cars that average 50 MPG is that this "standard[s] would save consumers $4,000 at the pump over the life of their cars. That's $1 trillion nationwide -- and more if gas prices rise."

My question is, "Would automobile manufacturers produce cars that average 50 MPG if the legal requirement does not exist? Let's assume that the $4,000 is the present value of the money consumers would save over the lift of the car when it meets the efficiency standard. What would happen if the government removes the standard? I see two possibilities.

1. If the cost to the manufacturers of meeting the standard is less than $4,000, then the manufactures would meet the standard and would increase the price of the car more than the cost and less than $4,000. Suppose that the additional cost is $3,500. By producing the car and charging $3,750 more for the car, both the consumer and producers gain. The consumers gain because the increase in price, $3,750, is less than $4,000, the present value of the money they save on gasoline. Producers gain because the increase in price, $3,750, is greater than $3,500, the additional cost they incur.
2. If the cost to the manufacturers of meeting the standard is more than $4,000, then the manufactures would not meet the standard. Suppose that the additional cost is $4,500. Consumers would not want to buy cars meeting the standard if the price increases by more than $4,500 because the increase in price is greater than the present value of the money they save on gasoline. Producers would not want to sell cars meeting the standard if the price increases by less than $4,500 because the increase in price is less than the extra cost they incur. 

The analysis indicates that the market would meet the fuel efficiency standards if the extra cost of meeting the standard is less than the present value of the money consumers save on gasoline and would not meet the standards if the extra cost of meeting the standard is greater than the present value of the money consumers save on gasoline. We can draw two conclusions.

1. When the cost of meeting the standard is less than the benefit consumers receive, then the market will produce cars that meet the standard without any need for government interference.
2. When the cost of meeting the standard is greater than the benefit consumers receive, then government interference increases the price of cars by more than the benefit consumers receive.