Reliable unit operations are key to the success of petroleum refiners. The introduction of opportunity crudes, typically those containing high levels of naphthenic acid and sulfur, present challenges to maintaining high unit reliability. These components in opportunity crudes can contribute to accelerated corrosion, both localized and general, often in locations that have been free of corrosion when processing less aggressive crudes. This paper will address steps that can be taken by refiners, such as the use of equipment monitoring envelopes, to minimize the potential for unexpected and unplanned incidents associated with processing of opportunity crudes.