HOUSTON, July 16 (Reuters) - Oil major Exxon Mobil (XOM.N) , opens new tab bought Mars crude for August delivery, two sources said on Wednesday, after briefly halting purchases of the flagship offshore grade due to a zinc contamination issue.

The zinc contamination in the Mars crude oil stream had pushed Exxon to borrow up to 1 million barrels of crude oil from the Strategic Petroleum Reserve for its Baton Rouge refinery in Louisiana.

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The start-up of an offshore well caused the zinc contamination in Mars crude, Chevron (CVX.N) , opens new tab said last week.

Chevron was actively working to resolve the issue, the company said on Tuesday.

Exxon and Chevron did not immediately reply to requests for comment on Wednesday.

The crude grade was trading at a 30-cent discount to U.S. crude at the Cushing, Oklahoma, hub, due to the persistent quality issue. That compared with a $1 premium at the end of June.

https://www.reuters.com/business/energy/exxon-restarts-purchases-mars-crude-after-brief-pause-over-zinc-issues-sources-2025-07-16/