Yes, the simple "rule of thumb" is "the resulting CO2 is 3 times heavier than the gasoline burned." Because chemistry. H weights "almost nothing" (in the engineering approximation sense, to the first order of magnitude) in hydrocarbons, and the weight of a single CO2 molecule (made of two oxygen atoms, one carbon atom) is roughly 3 times the weight of C atom alone (again as a good enough simple approximation, it's a little more, but C alone is a little lighter than O, so all together with the starting H, everything comes to 3).
For those who like more exact calculation: one molecule of C8H18 (octane) weights approx 8 * 12+18=114 masses of H, only that one molecule will produce when burnt 8 CO2 molecules, which weight 8 * 12+2 * 8 * 16=352, and 352/114 ~ 2.98 ~ 3
https://www.scientificamerican.com/article/experts-weight-ra...
For those who like more exact calculation: one molecule of C8H18 (octane) weights approx 8 * 12+18=114 masses of H, only that one molecule will produce when burnt 8 CO2 molecules, which weight 8 * 12+2 * 8 * 16=352, and 352/114 ~ 2.98 ~ 3