I noticed the brake fluid was a little low on MH and was going to add some when I notice what I have says DOT3 HIGH Temperature SYNTHETIC. Not knowing what the present fluid is will it make any dif...
All DOT 3, DOT 4, and DOT 5.1 is synthetic. Some brands just like to advertise it more, but they are all synthetic. So go ahead and mix any of those combos you want.
DOT 5 is silicone brake fluid and is NOT compatible with any of the other brake fluids.