What kind of transmission fluid do you need for a 91 Nissan 240sx?

For a 1991 Nissan 240SX, you typically need to use Dexron III/Mercon automatic Transmission Fluid for the automatic transmission. If you have a manual transmission, it's recommended to use a high-quality gear oil, such as 75W-90 or 80W-90, depending on the specific requirements. Always consult your owner's manual for the most accurate specifications and recommendations.