By the time Sears moved from Harden Street to Columbia Mall, it was long past the catalog glory days of being the company you could by anything from, but it hadn't yet been so bloodied in the retail wars that it would reject odd ideas out of hand.
This concrete slab in the Columbia Mall parking lot by the Charleston Crab House (and still actually owned by Sears to judge from the tow-away signs) was one of them. Over this slab was a canopy, and under the canopy was an island with a number of Sears-branded gas pumps. I don't remember a whole lot about the place as we only filled up one of two times there. I'm pretty sure it was self-serve, but since there was no such thing as electronic credit card reading pumps at the time, there certainly would have been a cashiers shed with an attendant. You could pay with cash, or, of-course, with your Sears Card.
My memory is that the place was an experiment that didn't last too long. I don't know exactly what happened, but I can hazard some guesses. First, the location was not convenient unless you were already at the mall. Getting in and out of the mall parking lot was (and is) much more time consuming than stoping at a corner station. Second, in the 70s people actually had some brand loyalty to different gas chains, and felt that name-brand gas was a better product than generic. Now we tend to think it's like sugar, and there's no problem buying Domino's if Dixie Crystals is more expensive. Third, at some point in the 70s (I believe) there was a major scandal about Sears's auto repair operation ripping people off (that's why about all they will do nowadays is change tires or batteries). The opprobrium from that may have tainted their gas business in people's minds. Fourth, it is simply the fact that selling gas was not in the core retail market Sears was (is..) trying to serve. As their fortunes declined, they may have decided that selling gas was a distraction and brand-dillution. (Though I have seen Wal-Mart trying the concept recently..).
At any rate, the place closed after not too many years. The canopy stood for several years after that, but was itself finally torn down. I don't remember the tanks being torn out, and there are still some access points, so perhaps they are still there (though that seems like an enviromental cleanup bill waiting to happen if it really is the case).