My Accent needs more brake fluid. Based on the manual, it can take FMVSS116 DOT-3 or DOT-4. I don't know whether it currently has DOT-3 or DOT4, so my question is:
Will mixing DOT-3 and DOT-4 fluids have a negative impact on brake performance?
DOT3 and DOT4 are compatible and can be mixed. The main difference between them is DOT4 has a higher boiling point, though it also tends to absorb moisture more readily.
What you don't want in the mix is DOT5 silicone-based fluid which is not compatible with the other brake fluids.
NO. Do not top up the fluid. The brake fluid level is supposed to go down as the fluid gets pushed through the brake lines as the pads wear thinner. When you put new pads on the level goes back . Brake fluid should not get depleted. But if you are losing some, and you have spongy brakes then you need to repair that issue, be it a leaky master cylinder or whatever.
If you haven’t changed your brake fluid in a while, flush out all the oil fluid & fill in new fluid.
Thank You Chuck for your answer!
Forgot to mention that I'd noticed my brake pedal was sinking a little recently. Going to try adding more fluid and see if that's all it needs.