How can I improve shift feel on an older manual transmission? Which Bell Hammer product should I use, and how much should I add if the gearbox uses 1.8L of 75W-90 oil?

LS Bell Hammer GOLD (concentrate) is recommended for improving shift feel on older gearboxes.
It forms a durable lubricating film on metal contact surfaces, helping reduce notchiness and making gear engagement smoother.

The recommended dosage is 5–10% of the total gear oil volume.
For 1.8 liters of 75W-90 oil, this equals approximately 90–180 ml.

After adding, normal driving will allow the film to form gradually, and the improvement in feel should become noticeable over time.