The catalytic converter and GM High Energy electronic ignition were advertised among the components of «Chevrolet's new Efficiency System» which was promoted to offer other benefits to owners of 1975 models versus comparable 1974 models that included extended maintenance
intervals from 6,000 to 7,500 miles (12,100 km) for
oil / filter
changes and spark plugs that lasted up to 22,500 miles (36,200 km)
compared to 10,000 miles (16,000 km) on»74 models.