Vertical spacing outside multline environment

Question

When using multline for parsing an equation, there's a larger vertical space above the equation than below. Why is this? It looks off. Example:

\documentclass{article}
\usepackage{amsmath}
\usepackage{lipsum}
\begin{document}

\lipsum[2]

\begin{multline}
    {I_{xx,\,\mathrm{frus}}} = {I_{xx,\,\mathrm{hemi}}} - {I_{xx,\,\mathrm{cap}}} \\ - \left({V_{\mathrm{cap}}} m_{\mathrm{frus}} {V_{\mathrm{frus}}}^{-1}\right) {\left( {{{\bar z}_{\mathrm{cap}}} - {{\bar z}_{\mathrm{hemi}}}} \right)^2} - m_{\mathrm{frus}} {\left( {{{\bar z}_{\mathrm{frus}}} - {{\bar z}_{\mathrm{hemi}}}} \right)^2}
\end{multline}

\lipsum[3]

\end{document}

Output:

Answer 1

Remove the blank line before the multline environment. It causes the previous paragraph to end, and a bigger vertical space is the result.

For that matter, you may wish to remove the blank line after the environment too, unless the context really does call for a paragraph break (i.e., change of topic).