These days, Frank Lemos manages a shipping operation, but the former truck driver still gets behind the wheel occasionally to train new drivers or to fill a staffing hole. When he does, he notices a big difference. The firm recently moved away from conventional diesel fuel, and now there's something missing: the permeating petroleum smell that drivers wear after a day inside a big rig. "You come home, and you don't get to just jump in bed if you're tired. You have to take a shower, or else someone's going to kick you out of bed," said Lemos, who is operations manager for Portland-based Titan Freight Systems.