Seems like someone posted about which fluid to use but I can't seem to find it.

My reservoir is low... the fluid looks clean, so I just want to add to it.

Any suggestions?

Use DOT3.....

I used Synthetic DOT3.

Make sure that your pure synthetic is not silicone...synthetic as silicone won't readily mix with non silicone brake fluid. Valvoline Syntec is a non silicone synthetic that will mix with regular dot 3. But it's best to use all one level.-dot 3- etc. until you flush and fill with a new level- like dot 4 Valvoline Syntec or equivalent. Stick to Dot 3 until your warranty runs out. Sine warranty work takes $$ out of the pockets of the service writers, they'll do anything they can to make you vs the company-pay...