@4xsample @elonjet I didn't know it myself. From:
https://www.epa.gov/energy/greenhouse-gases-equivalencies-calculator-calculations-and-references

" ... use a common conversion factor of 8,887 grams of CO2 emissions per gallon of gasoline consumed ... to obtain the number of grams of CO2 emitted per gallon of gasoline combusted, the heat content of the fuel per gallon can be multiplied by the kg CO2 per heat content of the fuel."

Now 1 gallon of gasoline is 3217 grams, so each gram of gasoline is going to create 2.7 grams of CO2.

@4xsample @elonjet section 2.2 of:

https://www.google.com/url?q=https://www.epa.gov/sites/default/files/2016-03/documents/stationaryemissions_3_2016.pdf

Goes in details of how different content of fuels affects the final number. I didn't read it thoroughly, but their formula takes into account other emissions like N2O and calculates the equivalent CO2 emissions.
Having said all this, I wonder whether conservation of mass seems not to apply, as the weight CO2 includes the weight of Oxygen which is not necessarily included in the weight of the fuel?