Systems and methods are provided for using field enhanced separations to produce multiple fractions from a petroleum input. A liquid thermal diffusion and/or electric field separation is used to produce the fractions. The fractions can then be used to form multiple outputs that share a first feature while being different with regard to a second feature. For example, a first fraction from the plurality of fractions can have a desired value for a first property such as viscosity index. Two or more additional fractions from the plurality of fractions can then be blended together to make a blended fraction or output. The blended fraction can have a value for the first property that is substantially similar to the value for the first fraction. However, for a second property, the first fraction and the blended fraction can have distinct values. As a result, multiple output fractions can be formed that share a first feature but differ in a second feature.