Problem shifting into 1st

I have a 1994 galant with a 5 spd and when down shifting or coming to a stop if I down shift into 1st before the car stops it will grind the gear. It has a fairly new clutch. Is it a good idea to run synthetic oil in the gear box? Also I get about 27 mpg with it any quick ideas for better mileage? Thank you for your time

I have a 1994 galant with a 5 spd and when down shifting or coming to a stop if I down shift into 1st before the car stops it will grind the gear. It has a fairly new clutch. Is it a good idea to run synthetic oil in the gear box? Also I get about 27 mpg with it any quick ideas for better mileage? Thank you for your time


you are not pose to downshift into first when the car is going at a certain speed, and that is your syncros not letting you go into gear.