The EQUA Carbon Monoxide Index

What is the issue?

Potentially fatal for humans as well as damaging to the environment, carbon monoxide is generally considered a problem primarily confined to gasoline vehicles. Regulations to control CO emissions distinguish between the fuel types, with gasoline vehicles legally allowed to emit twice as much as diesel vehicles. The EQUA CO Index reveals whether the statutory requirements are being met in real-world operation.

How the EQUA CO Index helps

The EQUA CO Index awards a common rating regardless of fuel type to allow comparisons between vehicles. Gasoline vehicles tested by Emissions Analytics on the road need to achieve a D-rating or better to match the requirements of the 3.4g/mi (5yr/50k mile) of the regulated limit under Tier 2 Bin 5. Similarly, diesel vehicles must meet the requirements of the Tier 2 Bin 5 NOx rating (5yr/50k mile) which is identified as a D-rating or better on the EQUA CO Index.

The EQUA Index is the definitive guide to vehicle emissions on the road, powered by Emissions Analytics, the independent testing and data analysis experts.

Use the table above to identify which cars are legally compliant in real-world operation from the extremely clean A rated models to F for those emitting many times more than the law allows.

Ratings Explained

Rating Lower bound1 Upper bound2
A 0.00 0.50
B 0.50 1.70 Meets California LEVIII ULEV50/70 standards and LEV II ULEV (5yr/50k mile)
C 1.70 3.40 Meets California LEVII LEV standards, LEV I Tier 1/TLEV/LEV/ULEV and EPA Tier 1, Tier 2 Bin 5 (all 5yr/50k mile)
D 3.40 4.20 Meets California LEVIII LEV160 standards, LEV II LEV, LEV I Tier 1/TLEV/LEV/ULEV and EPA Tier 1, Tier 2 Bin 5 (all 10yr/100k mile)
F 4.20 Above Tier 2 Bin 5 (10yr/100k mile) level
Units: g/mi, 1 exclusive, 2 inclusive