A fuel separation system (108, 400), comprising: a fuel separator (108, 418, 422) configured to receive a fuel stream (106, 406, 410) and separate the fuel stream (106, 406, 410), based on a volatility of the fuel stream, into a first vapor stream of relatively lower research octane number compounds and a combined liquid stream of relatively higher research octane number compounds; and a heat exchanger (404, 408) fluidly coupled between a fuel input of the fuel stream (106, 406, 410) and the fuel separator, the heat exchanger configured to transfer heat from the first vapor stream to the fuel stream, and output a heated fuel stream (406, 410) to the fuel separator and a second liquid stream of relatively lower research octane number compounds, wherein the fuel separator (108, 418, 422) comprises a first stage fuel separator and a second stage fuel separator, wherein the first stage fuel separator is configured to receive the heated fuel stream (406, 410) and separate the heated fuel stream (406, 410), based on the volatility of the heated fuel stream (406, 410), into a second vapor stream of relatively lower research octane number compounds and a third liquid stream of relatively high research octane number compounds, and wherein the second stage fuel separator is configured to separate the second vapor stream separated by the first stage fuel separator into an oxygenate stream and the first vapor stream from which heat is transferred by the heat exchanger (404, 408) to the fuel stream (106, 406, 410), wherein the combined liquid stream includes the third liquid stream from the first stage fuel separator and the oxygenate stream from the second-stage fuel separator. a fuel separator (108, 418, 422) configured to receive a fuel stream (106, 406, 410) and separate the fuel stream (106, 406, 410), based on a volatility of the fuel stream, into a first vapor stream of relatively lower research octane number compounds and a combined liquid stream of relatively higher research octane number compounds; and a heat exchanger (404, 408) fluidly coupled between a fuel input of the fuel stream (106, 406, 410) and the fuel separator, the heat exchanger configured to transfer heat from the first vapor stream to the fuel stream, and output a heated fuel stream (406, 410) to the fuel separator and a second liquid stream of relatively lower research octane number compounds, wherein the fuel separator (108, 418, 422) comprises a first stage fuel separator and a second stage fuel separator, wherein the first stage fuel separator is configured to receive the heated fuel stream (406, 410) and separate the heated fuel stream (406, 410), based on the volatility of the heated fuel stream (406, 410), into a second vapor stream of relatively lower research octane number compounds and a third liquid stream of relatively high research octane number compounds, and wherein the second stage fuel separator is configured to separate the second vapor stream separated by the first stage fuel separator into an oxygenate stream and the first vapor stream from which heat is transferred by the heat exchanger (404, 408) to the fuel stream (106, 406, 410), wherein the combined liquid stream includes the third liquid stream from the first stage fuel separator and the oxygenate stream from the second-stage fuel separator.