Super Stock tractor Open class uses primarily methanol fuel (some are diesel versions). The Super Stock Open machines can generate over an of torque, with billet or re-cast engine blocks. Super Stock Open and Super Stock Diesel tractors may use up to four turbochargers in three stages. The Diesel super stock tractors generate close to and of torque and are allowed to compete in the Open class, which very rarely occurs anymore. However, a true Open (methanol fuel) tractor is not allowed to compete in the Diesel class.