The subject invention provides microbe-based products, as well as their use to improve oil production and refining efficiency by, for example, remediating the disposable layers in oil tanks and other oil storage units. In preferred embodiments, the microbe-based products comprise biochemical-producing yeast and growth by-products thereof, such as, e.g., biosurfactants. The subject invention can be used to remediate rag layer and/or other dissolved solid layers that form in water-oil emulsions. Furthermore, the subject invention can be used for remediating solid impurities, such as sand, scale, rust and clay, in produced water, flow-back, brine, and/or fracking fluids.