You're taking a bunch of `C` in the tank (AMU: 12) and 2x `O` out of the atmosphere (AMU: 16). This means the expected mass goes from 12 -> 44, or an increase of 3.6. My trusty calculator says that takes .71kg to 2.6kg.
This is just approximate, since fuel has a bunch of H and S and other crap, so it's not 100% C. But, yes, these figures are in the right ballpark.
You are correct of course. I was intending to make an alchemy joke about a particular phrasing of the parent poster (the part about creating 1 tons of "carbon"), but misread the entire message and commented on the wrong part. :-/
This is just approximate, since fuel has a bunch of H and S and other crap, so it's not 100% C. But, yes, these figures are in the right ballpark.