System always used DOT 3, new replacement master cylinder uses DOT 4

1987 CHEVROLET VAN
31,000 MILES • 5.0L • V8 • 2WD • AUTOMATIC
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CSTRAUSER
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Changing the master cylinder in my Van listed above (g20), the whole system always used dot 3. so i filled the new reservoir with dot 3 and when i was about to mount it on i went to put on the cap and it says use DOT 4. why the change? the part is identical, and i am assuming because it is newly manufactured it uses dot 4, but will DOT 3 be okay in this case? for its entire life up until this point its always been dot 3.
Aug 31, 2019 at 1:24 PM
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SCGRANTURISMO
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Hello,

It should be okay. DOT 3 and DOT 4 brake fluid is compatible with the difference being that DOT 4 brake fluid offers a higher boiling point than DOT 3 brake fluid.

Thanks,
Alex
2CarPros
Aug 31, 2019 at 2:02 PM
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