Mobil Corp. has begun a boycott of the Wall Street Journal, pulling all advertising from the newspaper and instructing employes not to talk to the paper's reporters.

The new Mobil policy was recently approved by the company's top management and extends to all of Mobil's operations "worldwide," according to company spokesman John Flint. He said Mobil has also stricken the Journal from its mailing list for press releases.

"Our company takes the position that we won't have anything to do with the Wall Street Journal," Flint said. "Specifically, we will not answer their questions on or off the record, provide them with any data or grant any interviews."

Mobil currently places about $500,000 worth of advertising in the Journal each year, almost all of which are company-written opinion columns and which now will be terminated, Flint added.

Flint said the new policy comes after "five years of problems with working with the Journal." He refused to elaborate. Stewart Pinkerton, assistant managing editor of the Journal, said he had "no idea" why Mobil had chosen to take the action.

"We're not going to respond," Pinkerton said. "We're going to continue to do our job and cover the oil industry and Mobil's part in it."

Two Journal reporters said yesterday that Mobil's action was triggered by a Nov. 16 story reporting that Mobil was building a $300 million Chicago office tower with Galbreath-Ruffin Corp., a real estate company that employed a son-in-law of Mobil Chairman Rawleigh Warner Jr.

The story, quoting from a Mobil proxy statement, stated that Mobil had agreed to the real estate company's request to transfer a "small part" of its shares in the joint venture project to Percy R. Pyne IV, Warner's son-in-law. It also quoted Mobil's proxy statement and a company press release as saying that Pyne would participate in leasing the new office building and would be compensated on a commission basis.

Richard B. Schmitt, coauthor of the article, said that Flint called him that day and told him "Mobil was very angry at me and my colleagues, and he particularly cited the coverage we gave to the real estate company."

Flint did not dispute any of the facts in the story, according to Schmitt, but complained that the company had sent the reporter three press releases that day and that the only one the paper chose to write about was the one involving Pyne.

Pyne said yesterday that he is a senior vice president of Galbreath-Ruffin and had been working on the Chicago office project for four years. "I have gotten to a place in this industry with a lot of hard work," he said.

Schmitt said that Flint also complained because the Journal story reported that a group of companies controlled by the son of William P. Tavoulareas, the former president of Mobil, received about $1.67 million in management fees from five corporations in which Mobil holds minority interests.

Business transactions involving Mobil and Atlas Maritime Co., a London-based shipping firm partially owned by Tavoulareas' son, were reported by The Washington Post in November 1979 and became the subject of a $50 million lawsuit by Tavoulareas and his son against the newspaper. A $2.05 million judgment against the Post awarded by a jury in 1982 was struck down last year by U.S. District Court Judge Oliver Gasch. Tavoulareas is appealing the decision.