Can 80W-90 gear oil be used in place of 75W-90?

Yes, 80W-90 gear oil can generally be used in place of 75W-90 in certain applications, but it's important to check the manufacturer's specifications. The main difference lies in the viscosity at lower temperatures; 75W-90 is better suited for colder conditions. If the application involves extreme temperature variations, sticking to the recommended grade is advisable for optimal performance and protection. Always consult the vehicle's manual or a professional if unsure.