Embodiments include systems and methods of in-line mixing of hydrocarbon liquids and/or renewable liquids from a plurality of tanks into a single pipeline based on density or gravity. According to an embodiment, a method of admixing hydrocarbon liquids from a plurality of tanks into a single pipeline to provide in-line mixing thereof includes initiating a blending process. The blending process including continuously blending two or more liquids over a period of time, each of the two or more liquids stored in corresponding tanks, each of the corresponding tanks connected, via pipeline, to a blend pipe thereby blending the two or more liquids into a blended liquid. The method further includes determining a density of each of the two or more liquids to be blended during the blending process. The method includes, in response to a determination that the blend process has not finished and after the passage of a specified time interval, determining an actual blend density of the blended liquid, via a blend sensor connected to the blend pipe, the blended liquid flowing through the blend pipe and in contact with the blend sensor, and the specified time interval less than a total duration of the blending process. The method includes determining an actual blend density of the blended liquid, via a blend sensor connected to the blend pipe, the blended liquid flowing through the blend pipe and in contact with the blend sensor, and the specified time interval less than a total duration of the blending process; comparing the actual blend density with a target blend density; and in response to a difference, based on the comparison, of the actual blend density and target blend density determining a corrected ratio based on each density of the two or more liquids, the actual blend density, and the target blend density and adjusting, via one or more flow control devices, flow of one or more of the two or more liquids, based on the corrected ratio.