High-pressure phase behavior data are reported for statistically random poly(ethylene-co-20.2 mol %-1-butene) (PEB10) in ethane and deuterated ethane from ambient temperature to 155 degrees C and pressures to 130 MPa. The two cloud-point curves exhibit negative slopes in pressure-temperature (P-t) space with the PEB10-deuterated ethane curve at higher pressures than the curve in ethane. Data are also reported for statistically random deuterated PEB10 (d-PEB10) in n-pentane, isopentane, neopentane, and cyclopentane. Solvent quality orders as cyclopentane > n-pentane >= isopentane > neopentane, which is also the same ordering of the solvent critical temperatures. The d-PEB10-cyclopentane cloud-point curve has a steep positive P-t slope of approximate to 0.28 MPa.degrees C-1 near 200 degrees C. The d-PEB10-n-pentane and isopentane curves also have positive P-t slopes of approximate to 0.16 MPa.degrees C-1 at temperatures between (approximate to 100 and 200) degrees C and pressures to approximate to 15 MPa. The curve for the d-PEB10-neopentane system is virtually flat at a fixed pressure of approximate to 20 MPa from (200 to approximate to 30) degrees C, where the curve changes abruptly to a positive slope of approximate to 1.65 MPa.degrees C-1. The positive-slope portion of this cloud-point curve represents solid + liquid to fluid transitions where the neopentane is the solid phase not the d-PEB10, which is amorphous.