The effectiveness of copolymer depressing dopants in straight-run and degraded oil fractions, namely, the 180-350A degrees C straight-run diesel fraction, 275-400A degrees C oil fraction, and the extract of its selective purification, vacuum gasoils, and products of delayed coking and catalytic cracking is investigated. It is shown that marine oils with improved low-temperature properties can be obtained by adding to these fractions copolymer depressing dopants in optimal concentrations.