If your only choice is a gas station with the islands perpendicular, I've found that there may be room to pull in from the building side giving you a straight exit out if you use the end island near the facility exit. This also keeps you from blocking the facility entrance. Make your turns wide to allow for the fiver tracking inside of your TV.
But I try to pick highway exits that have multiple gas stations so I have a selection to scope out.
Top off fuel whenever there is opportunity even if you are only down a quarter tank.