The Post performs a disservice to its readers by reporting only the automakers' cost estimates to achieve the 48 percent increase in fuel-efficient vehicles during the next decade {"Higher Mileage Standards Run Out of Gas in Senate," news story, Sept. 26}.

According to a study by the American Council for an Energy Efficient Economy, the fuel-efficiency improvements would add several hundred dollars to the price of a new car. However, these costs would be recouped within three years, and an additional $1,000 would be accrued during the next seven years because of savings at the gas pump.

This 33 percent return on investment far exceeds the return on the Dow-Jones average, money market funds or Treasury certificates.

Most important, the improvements do not require down-sizing of cars, and theymaintain or improve safety standards and emission controls as well as other consumer amenities like acceleration. The Senate's buckling under pressure from the auto industry flies in the face of the leadership this nation now demands to free us from oil tyrants like Saddam Hussein.

When consumers know that we can save money and cut foreign imports, they will demand the passage of fuel-economy standards.

MICHAEL TOTTEN Washington The writer is legislative aide to Rep. Claudine Schneider (R-R.I.).