The world's most closely watched stock index will get a slightly new look at the end of August, as Exxon Mobil Corp is bumped out of the blue chip Dow Jones Industrial Average, the index's parent company announced Monday.

The global oil giant will be removed to make room for cloud computing firm Salesforce.com, S&P Dow Jones Indices said in a statement.

It is a historic change for the index, as Exxon has formed part of the Dow since October 1928, although for years it was listed as Standard Oil of New Jersey.

In addition, biotech company Amgen will replace pharmaceutical giant Pfizer, and industrial systems manufacturer Honeywell takes the spot held by defense contractor Raytheon Technologies.

Exxon Mobil has been in the Dow index since 1928 but now will be replaced Exxon Mobil has been in the Dow index since 1928 but now will be replaced Photo: AFP / Saul LOEB

The change is driven in part by Apple's planned four-to-one stock split, which reduces the Dow's weight globally, S&P Dow Jones said.

But the changes also will "help diversify the index by removing overlap between companies of similar scope and adding new types of businesses that better reflect the American economy."

The new index will debut August 31.