Asphaltene precipitation in dead crude oil can occur not only by adding saturated solvents such as heptane but also occurs at elevated temperatures. In this work, the relation between asphaltene self-precipitation onset and refractive index (RI) at elevated temperatures is investigated. Experimental measurements of RI for three crude oils are reported at different temperatures. Determination of RI at the onset of precipitation showed that that precipitation occurred at a characteristic RI of 1.42 for each crude oil. The asphaltene content of these samples were in the range 1-11.6 wt %. The sizes of the asphaltene particles formed at elevated temperature were smaller than those formed upon solvents addition.