Muskat refined Darcy's equation for single phase flow, and this change made it suitable for the petroleum industry.

Based on experimental results worked out by his colleagues, Muskat and Milan W. Meres also generalized Darcy's law to cover multiphase flow of water, oil and gas in the porous medium of a petroleum reservoir.

He took a one-year break from Gulf, during World War II, to serve as chief of the Acoustics Division of the Naval Ordnance Laboratory.

In his later years Muskat withdrew from professional life and relocated to Pasadena, California, where he died on June 20, 1998, at the age of 92.

Another problem that faced Muskat and his colleagues, is that an oil reservoir has large horizontal dimensions, and production wells are spread all over it.

Large emphasize is put on discussing results of experimental analogues such as heat flow and electric current.

Muskat, with assistance of geophysicist Milan W. Meres (1906–1963), analyzed results from the steady-state and the transient flow experiments of Ralph Dewey Wyckoff and Holbrook Gorham Botset.

[4] The formulation is based on Muskat's theory that the porous medium has a local structure of macroscopic size that is defined by the saturations, or volume fractions, of the fluid mixture.