(Reuters) - Sirius XM Holdings Inc (>> Sirius XM Holdings Inc) raised its full-year forecast for revenue and subscriber additions for the second time in a row, citing strong U.S. auto sales.

Sirius XM said it now expects to add 1.8 million net new subscribers this year, up from its prior forecast of 1.4 million. The company had first forecast addition of 1.2 million subscribers in January.

People who buy new cars fitted with Sirius receivers usually get free access for a few months, but must pay a fee to continue the service.

Auto sales in the United States have been healthy in the first six months of the year, with consumer demand for new vehicles strengthening. U.S. auto sales are expected to rise about 5 percent this year.

The company also raised its revenue forecast for 2015 to $4.5 billion from $4.47 billion earlier. This was largely in line with analysts' expectations of $4.49 billion, according to Thomson Reuters I/B/E/S.

Sirius XM said it added 692,000 net new subscribers in the second quarter, more than 45 percent increase from a year earlier.

The company's net income fell to $102.8 million in the second quarter ended June 30, from $120 million a year earlier, due to the settlement of certain royalty litigation during the quarter.

Earnings per share were flat at 2 cents, the company said. Excluding items, the company earned 3 cents per share on revenue of $1.12 billion, both of which were in line with analysts' estimates.

Shares of Sirius XM, which competes with music streaming services such as Pandora Media Inc (>> Pandora Media Inc) and Spotify, rose 3.6 percent at $3.98 in premarket trading. Sirius' stock had gained about 10 percent this year through Monday close of $3.84.

(Reporting By Lehar Maan in Bengaluru; Editing by Simon Jennings and Anil D'Silva)

Stocks treated in this article : Pandora Media Inc, Sirius XM Holdings Inc