By Janet Raloff
A poorly running car engine can spew unburned hydrocarbons out the tailpipe. Although this waste of fuel dirties the air and costs the motorist money, many people don’t recognize signs that a tune-up is long overdue.
Colorado scientists now report one successful remedy: gentle warnings from a friendly, personalized billboard.
In the United States, “about 6 percent of the cars are responsible for half the [auto] pollution,” notes University of Denver chemist Gary A. Bishop. Finding them can be hard, he says, because most are not old clunkers.