We have enough data to estimate the reasonable range of possibilities and exclude the upthread assertion that a ten minute car ride is similar emissions to 10k plastic bags. A degree of uncertainty need not make us helpless in the face of loud ignorance, that's how we end up giving equal weight in the media to common consensus of professionals in whatever field and political operatives with fringe beliefs but no evidence.

Sorry, I screwed up and misread what you wrote- primarily, a simple "we can do way better than 30mpg." And theres not a lot in the way of wiggle room to debate with any integrity the amount of CO2 burning a set quantity of gas produces. A couple percentage points for NOx and friends and thats it.

I am confused why everybody mentions emissions though. In a discussion on paper/plastic/reusable bags, in a response to a call for napkin math for a claim of "10,000 bags from the fuel needed to get to the store" (essentially the argument made)- CO2 isn't relevant: just the mass of the gas used to get to the store.

I'm not pleased with how this turned out. to be told I'm wrong? That's fine, its the internet. I'm disappointed and alarmed with how badly wrong the suggested corrections are... it's deeply frustrating for me as well.