Exxon Mobil is set to report its first-quarter earnings on May 1, before the market opens, giving investors a fresh look at the company's handling of a volatile start to the year. The company expects changes in liquids prices to lift first-half earnings by $1.9 billion to $2.3 billion compared with the fourth quarter, while gas prices could add another $200 million to $600 million. However, Exxon warned that higher oil prices were only one part of the earnings story due to market, planned, seasonal, and Middle East-related factors that could make the headline results harder to read. The largest swing item appears to be timing effects tied to trading and inventory accounting. Exxon also faces a production and refining issue tied to the same geopolitical tensions that helped lift oil prices.