I was searching the internet for data on greenhouse gas emissions from various electric vehicle models, when I stumbled upon this calculator of upstream emissions (those generated when producing the electricity used to charge the car) and tailpipe emissions (zero for electric vehicles) on a Department of Energy webpage: https://www.fueleconomy.gov/feg/Find.do?action=bt2.

I was shocked to find that for a Chevrolet Blazer EV 2024 (https://www.fueleconomy.gov/feg/Find.do?year=2024&vehicleId=47445&zipCode=77058&action=bt3), the total emissions of 411 g CO2/mile on average across different power grids in America actually exceeds that of an “Average New Gasoline Vehicle,” which is stated as 400 g CO2/mile. Does this mean that this electric vehicle actually generates more greenhouse gases per mile driven than a conventional car when you factor in the electricity production? Does this not contradict other data I have seen estimating that this vehicle has an MPGe in the 90s or higher, which exceeds the typical MPG in the 30s range for conventional cars? Surely the manufacturing emissions for this electric vehicle would also exceed that for a gas-powered car, so does this mean the total emissions for the vehicle across its life cycle would also be higher than for a regular car?

To further confuse me, I saw that the Chevrolet Bolt EUV 2023 (https://www.fueleconomy.gov/feg/Find.do?year=2023&vehicleId=45750&zipCode=77058&action=bt3) has a significantly better profile, producing about 126 g CO2/mile on the average American electricity mix. What might account for the drastic difference between the upstream emissions for the Blazer and the Bolt? Is it the fact that the Blazer is heavier, which means more electricity and thus more greenhouse gases are required to propel the vehicle 1 mile? Or are there other factors?

Overall, I just want to buy an electric vehicle that truly has low life cycle emissions, and I am having trouble interpreting the data. Please let me know if you all have any good sources you use.