1990 Tier 1 exhaust emissions standards for 1998 - 2003 gasoline passenger cars and light light-duty trucks are as follows (first 50,000 miles/5 years):
HC: 0.25 grams/mile
C0: 3.4 grams/mile
NOx: 0.4 grams/mile
The Tier 2 regulations are being phased in from 2004 to 2009. They are much more complicated.
