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Hey guys, did a service on my car a few days ago.
when changing to gearbox oil i accidentally spilt half a bottle.
Thus i only put 1.5 quarts of gearbox oil in.
Will this cause any problems or damage?
Obviously it would be ideal to just go get another bottle and top it up, but finances and time are rather limited right now, so i would prefer not to unless it will indeed cause trouble.
Sorry for what might seem like a noob question, dont have much experience with cars.

The Mazda MX5 NA8 Owner's Manual states manual transmission capacity is two litres.

Probably best to top it up.
You might get away with it, you might not. Gearbox oil is cheap for a small bottle.

2 litre box
1 litre diff.

Not that you measure, just pump it in until it dribbles out the fill hole.

4 litre bottle of oil is about $30 and will do the diff and box with a bit to spare

looks like i had better buy some more oil and fill it to the top i guess.

also can anyone tell me if i need to replace the shifter oil as well?
i assumed the gearbox and the shifter base would be connected but this video shows otherwise. just not sure if it would be the same for a 99 nb 5speed
https://www.youtube.com/watch?v=YmbN5JTeiNQ

Gearbox
Use GL-4 grade oil (75-90)
Requires about 2litres

If 5 speed, you should suck out and replace the turret oil
If 6 speed, you do not need to replace turret oil.

Draining:
Remove the FILL plug first, then remove drain plug.

Filling:
Fill until oil spills out the fill hole.
You can only fill a 5 spd via the fill hole.
You can fill a 6spd from the turret or via the fill hole.

Diff
Use GL-5 grade oil (75-90)
Requires about 1litre

Draining:
Remove the FILL plug first, then remove drain plug.

Filling:
Fill until oil spills out the fill hole.

Not much! Anecdata follows ...

Broke the racecar gearbox (6-speed) on the dyno recently, after an extended session (nice of it to wait ). Couple of other things made me wonder whether it was the gearbox, or/and something else. So when I got the car home, I put it up on the stands and drained the gb oil through a flyscreen mesh, to see what/if anything came out in the oil ... nothing in the oil, oh wait, actually, no oil either ...

I measured approx. 1/3 cup of oil came out of the gearbox, no gb oil outside the box, no oil stains under the car, no gear oil smell, no idea when/how the oil disappeared. It was installed 8 years ago, filled with Redline.

I do not recommend under-filling your gearbox, but on this experience the gearbox seems remarkably tolerant of low oil.