cash for clunkers

if cash for clunkers is really that popular, and beneficial for environment then is it not that the limit for eligibility should be raised from 18 mpg to 20 or 22 mpg?america is known to do things in big way then why just punny efforts for environment and not large effective efforts than just 2 hours of no cars scenario?

it is the only programme that has directly benefitted people from stimulous money. people will definately trade in these gas guzzler cars if they get good rebate and buy fuel efficient new cars.

also it shuld be regular programme to give some rebates to replace old cars say(25  years) as is done in some countries. this will also boost the regular sales of automobiles and help people toafford and help evvironment.