I heard in the news today that California tests vehicle emissions
for CO2. This sounds insane to me. The main reaction in an engine
is petrol + oxygen ==> water + CO2.
So in order to reduce CO2 emissions you must either make your car
less efficient (eg. produce some C instead), or use less petrol
(ie. **** up your A/F ratio, or get a smaller engine).
None of those options sounds too appealing to me.
How do cars with large engines (eg. 6L) pass?

(Let's not get started on whether CO2 emissions are a good thing or
not..)