Mixing brake fluid????

I'm installing a new lift and adding extended brake lines. I know I'll need to bleed the brake system and refill the reservoir/watch it after each wheel. I bought 1 bottle of DOT 3 synthetic brake fluid and asked the counter guy if I can just add it to my existing fluid and he kinda just nodded it off like whatever yeah. So I'm asking you guys. Is it ok for me to do that? My jeeps a yr old and has whatever came from the factory

You should be ok, but if you want to feel better buy the big battler and just flush all the fluid from the brakes....
Is a 2 man job
You need to add fluid than pump the brake add more fluid keep pumping the brake etc....
You're done when the fluid is all clear. Top the reservoir and bleed the system

I mixed Dot3 and Dot4 no issues, I meant to flush the system and use just one but that was 3 years ago and brakes work just fine.

Ok thanks guys