Investing.com - In just two years, China has become a major customer of U.S. oil companies, but that could change quickly if the trade skirmish between the two countries escalates.Among the next round of products facing a 25% Chinese tariff is crude oil.China is now the second largest market for U.S. oil exports, according to the U.S. Energy Information Administration.In the first fourth months of 2018, about 20% of U.S. oil exports went to China.Since the U.S. dropped restrictions on oil exports in late 2015, exports to China have increased 15-fold to about 330,000 barrels a day.Energy analysts say U.S. producers may be able to find alternative buyers, but probably at lower prices than the oil-hungry China is willing to pay.