Mike Wirth, executive vice president for Chevron’s refining and chemicals arm, said strong demand for refined products from Latin America as well as Asia in the past few months led to margins that were a bit stronger than many people expected.

“It’s ill-advised to believe that any renaissance in margins will sustain for a long period of time,” Wirth said.

“So we tend to plan and prepare our business for a pretty lean-margin environment, which is what the industry has seen on average over the long haul.”

As long as countries build refineries to ensure a security of supply, as in Vietnam, or in an effort to create jobs, the market for refining crude would remain oversupplied, he said.

“Long term, I think the fundamentals are still pretty tough for the downstream business,” Wirth said in an interview on the sidelines of the Milken Institute Global Conference in Beverly Hills, California.

Chevron’s three big US refineries are being shaped up to compete in the tougher market. A downstream arm restructuring launched last year will lead to a total of 2,800 job cuts by the end of this year, including 1,100 in the US.

“It’s the right fit and the right structure for our company,” Wirth said. “Notwithstanding this brief improvement in margins, I don’t think we’d do anything differently if we were to do it over again.”

On Friday, Chevron posted a 36 percent rise in earnings to $6.2 billion, driven by oil prices. Its downstream arm earned $622 million, up threefold on a year ago.

The second-largest US oil company, based in San Ramon, California, is investing in lubricants and petrochemicals in an effort to reduce the downstream reliance on refining, he said.

Chevron announced plans in January to build a $1.4 billion plant in Mississippi to double its capacity for premium base oil, the main ingredient in high-end motor oil.

Wirth pointedly praised Mississippi as a “great place to do business,” having faced years of environmental litigation in the company’s home state that stalled an upgrade to its oldest refinery in Richmond, north of San Francisco.

Wirth was at the conference to join a panel discussion on energy security that includes a former head of the US Central Intelligence Agency, Canada’s ambassador to the US, and oil man-turned-natural gas promoter T. Boone Pickens.

But Wirth, reiterating Chevron’s view that the scale of the energy supply problem will require a wide variety of sources, had personal insight into the challenge ahead for the Pickens plan to increase the number of trucks running on natural gas.

Wirth started his career with Chevron as a design engineer in the early 1980s, and recalled building natural gas filling stations in Texas and California more than 20 years ago.

“I remember the grand opening with great fanfare. We had government officials, and people from various businesses and regulatory agencies there,” he said in the interview.

“Over the ensuing months and years, as I returned to those stations, there wasn’t a lot of demand, there weren’t many customers,” he added. “And those stations aren’t actually in service any more because there was no market.”

Yet he believes Chevron, with its pipeline network and goal of increasing US natural gas output, would be a part of any such plan, so long as the investments are made in equipment to allow for rapid refueling at stations and incentives can make up for the limited global resale market for converted trucks.

Some of Chevron’s strongest oil and gas production growth will be from natural gas shipped out of huge deposits off the coast of Western Australia to Asian buyers, starting in 2014.

Asia-Pacific will also drive much of its downstream growth, helped by existing partnerships through its Caltex division.

Wirth, a former top Caltex executive based in Singapore for many years, said while it varied between countries, having a good partner was “essential” for operating in much of Asia.

He said Chevron now had the assets it needs in Asia, including a Singapore refinery that is a joint venture with PetroChina, and the massive Yeosu refinery in South Korea that is jointly owned with GS Holdings Corp.