After a selloff on Monday, oil prices bounced back at the start of trading on Tuesday.(Click to enlarge) (Click to enlarge) (Click to enlarge) (Click to enlarge) Reader Alert: Make sure you don't miss out on tomorrow's new and improved Oil & Gas Insider, with two breaking columns on the brewing crisis in Venezuela and the multi-billion-dollar bet China has made on Maduro. Sign up today for your free trial. - Gasoline margins have plunged in recent months as the glut of supply continues to worsen. - Refiners are churning out diesel because…