unmodified

US /ˌʌnˈmɑː.də.faɪd/
UK /ˌʌnˈmɑː.də.faɪd/
1.

chưa sửa đổi

not having been changed, especially in a way that is intended to improve something:

:
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The biofuel can be mixed with petroleum diesel and used in unmodified diesel engines.