U.S. oil and gas major Exxon Mobil signaled on Tuesday that its second-quarter earnings could see a boost of about $5 billion compared to the previous quarter, as oil prices spiked during the U.S.-Israeli war with Iran and the company's refining margins also improved. Investors scrutinize Exxon's earnings snapshot for signals on how oil firms will perform when they release second-quarter results. The conflict in the Middle East that began in February injected a hefty geopolitical risk premium into oil markets. For months, it virtually shut down the Strait of Hormuz, which carries about a fifth of global oil flows.