Gear Oil:
@haceeb,
You said that your car manual tells you to use API GL-4, however zic gear EP has different viscocities eg SAE75W80, 80w90, 80W, 90, 140.
On the other hand Zic Gear FF has only one viscocity ie SAE 75W85 and the dealer who was selling the product said that FF is made for car gears.
I should mention here that when I read the Zic catalog it said:
Gear FF: provides outstanding performance in most gear applications and that it meets the specifications of various passenger cars that are in mild, moderate and severe conditions.
Gear EP: provides outstanding performance in most gear applications meeting many service gear oil needs of Passenger cars, Trucks and Buses and other vehicles that are in moderate service conditions.
both ZIC FF and ZIC EP are API GL-4
SUMMARY: I think the ZIC FF will be a better option for your car and as you said that gears of your car became harder I think the ZIC FF will be a better choice.
I hope this helps
Thanks