The stability of 44 nm diameter silica particles in poly(ethylene glycol) (PEG) melts is assessed through the experimental measurement of particle second virial coefficients, B-2 = B-2,B-cc/B-2(HS), where B-2,B-cc is the particle second virial coefficient and B-2(HS) is the excluded volume second virial coefficient of the particles. Measurements are made using side bounce ultra-small-angle X-ray scattering (SBUSAXS) of dilute filled PEG melts of variable molecular weight. Results show B-2 values to be equal to or greater than one for the molecular weights investigated. Experimental results are compared to recent PRISM theory adaptations to filled polymer melts.