* Your car's specifications: Different cars have different gear ratios. Your car's owner's manual will provide the best guidance, often including a suggested shift point chart.
* Engine RPM: You generally want to shift into 5th gear when the engine is within its optimal power band in that gear. Going too low will cause lugging (straining the engine), while going too high will mean you're not utilizing the engine's efficiency. This optimal RPM range will vary by car, but is typically in the mid-range.
* Driving conditions: Steeper inclines require you to be in a lower gear to maintain speed and avoid lugging the engine. Conversely, on a flat road you can shift into 5th at a lower speed.
* Driving style: Aggressive driving may involve shifting at higher RPMs, while more fuel-efficient driving will prioritize lower RPMs.
Instead of focusing on a specific speed, pay attention to your engine's RPMs. Learn the optimal RPM range for your car in 5th gear and shift accordingly. Your car may have a tachometer (RPM gauge) to help you with this. If you're unsure, consult your owner's manual.
