I'm not so sure. Probably you couldn't do it with any sort of efficiency. Perhaps more importantly though, I haven't heard of many *effective* long-term CO2 sequestration strategies - we're going to need to store this stuff for at least a few centuries after all, to buy ourselves some time to come up with more permanent solutions. Trying to pump it into abandoned oil or gas wells hasn't been very successful - after a few years it just starts leaking out again over many square miles, and fracking makes it much worse. Storing it undersea is a non-starter - it creates giant dead zones in one our planet's most important ecosystems, and dissolves into the surrounding water, increasing ocean acidification and probably decreasing the ocean's normal uptake of atmospheric CO2 by a similar amount. The only one I've heard of that make any sense is creating biochar and burying it as a soil enrichment additive. But at that point, why not just make biofuel instead and pay the costs up front, instead of loading our cars with giant compressed-gas bombs and inviting various exploits of the CO2 recycling system?
Out of curiosity, let's run some numbers on efficiency of CO2 compression:
First off you run into the issue that a gallon of gas produces about 20 pounds of CO2 (or about 3.17lb CO2 per lb gasoline), so if you burn through a 15 gallon tank of gas you'll be increasing the mass you're carrying by 2.17* (15G*6.3lb/G) = 205lbs. Not a *lot*, but enough to have a measurable impact on efficiency.
Then there's the question of how much energy it takes to compress the CO2. To make it simple lets assume we first produce all the CO2 at atmospheric pressure, and then compress it. I think that should work out the same (or better) than the continuous-flow model. The relevant equation is W=nRT ln(V2/V1).
R=1.986Btu / lb-mol / *R (seems the most applicable availble on the wikipedia page, since for some damned reason I decided to do this in American units)
CO2 is 10.3 moles/pound, and there's 453.59237lb-mol per mol, so n = 305lb*10.3/454 = 7lb-moles of CO2
And it's ~0.12lb/ft^3 at NTP (normal temperature and pressure), so V1 = 305/0.12 = 2,542 ft^3
Finally the temperature at NTP = 70*F, or 530R
That leaves only the size of the storage tank, V2, to decide on. Lets say we make it the same size as the gas tank at 15gal=2ft^3
So the total (ideal case) energy to compress it will be
W=7lb-mol *(1.986Btu/lbmol/R) * 530R * ln( 2,542ft^3 / 2ft^3)
= 52,663 Btu
Huh, a lot less than I expected. And a gallon of gas typically contains ~114,100 Btu, though assuming compression is powered by engine with it's horrible ~25% efficiency, we're talking about burning 1.85 of those 15 gallons of gas just to compress the CO2. A 12% efficiency loss off the top - unfortunate, but surmountable. So I guess the only real problem is sequestration.