Had replaced the brake fluid (in reservoir + brake lines) with Motul DOT4 racing fluid at 45000 miles due to soft brake feel/excessive space before strong brake clamp. The braking force immediately felt stronger and much more responsive almost immediate. However, that braking force and the fluid color deteriorated after two years. After a second replacement and air flush, there is still 1-1.58n. of "play" in the brake pedal before clamping force is felt on the brakes. The Si can definitely use more aggressive sports or track brakes.