I am sure the fluid it DOT3, can I flush out the fluid and put in Silicone or synthetic?

I've never heard of "synthetic" brake fluid. Silicone, you don't really want to. Do a search on DOT5 for some other recent discussions on this.

I just throw ATE blue or gold in everything. Seems to work

Valvoline synpower fluid, its specs are as good or better than Ate blue/gold, costs much less, and is easy to get. On the other extreme we use Castrol SRF in the racecars

Good stuff that ATE blue or gold high boil point and because of the color you can tell when all the old fluid is gone when you flush the system.

I'm with TimT on the Valvoline brand. You can get that almost anywhere off the shelf, priced right too.

Thanks, so what are the prices?

ATE super blue runs about $13-$14 per one liter can.

How much do I need?

One can of ATE blue or gold is more than enough

Now I just need to find it

The valvoline runs about 8 bucks or so per 1 liter can. If you are doing a full flush, might as well get 2 liters