BOSTON -- Boston's iconic CITGO sign will go dark this Friday, as the oil company that owns it plans to change the light bulbs on the sign that overlooks Kenmore Square and Fenway Park.

The landmark sign will remain dark for two months.

The sign has stood high above the Boston skyline since 1940, when it was erected on what was then a regional office for the Cities Services oil company. In 1965, the lighted logo was changed to read CITGO. The building currently houses the Boston University bookstore.

"Its pulsing flash in the night sky has even been used by mothers-to-be at nearby Beth Israel to time their contractions," the company's website claims.

All 218,000 LED lights on the 3,600-square-foot sign will be replaced. The new lights are designed to better withstand high winds and extreme temperature variations.

More than 9,000 feet of lights on the sign were replaced five years ago to save on energy costs but those bulbs are now out of production.

The sign stands some 1,200 feet from home plate at Fenway Park – more than twice the distance of the longest home run ever hit there.

The sign did go dark in 1979, at the urging of Massachusetts Gov. Edward King, as a symbol of energy conservation. The sign remained dark for four years until it was relit at the urging of local residents.

CITGO did not wait until the baseball season was over this year, though the company's statement -- with a bit of optimism about the Red Sox prospects -- promised to have the sign relit in time for the playoffs.

CITGO, now part of a company owned by the Venezuelan government, changed the bulbs just five years ago when the old neon tubes were replaced with LEDs. CITGO said it is making the latest change as part of marking its 100th anniversary.