I have a 1990 2.8 Fourtrak. I recently bought and MOTed it after it had been sat up in a field for nearly 2 years. Everything is working fine, but the break fluid looks a bit iffy in the reservoir. On the cap it says to use DOT-3 break fluid, I was wondering if I can use DOT-4? I want to drain and replace the system, but only have DOT-4 at the garage. Please Advise.