Here are the engine options available for the 2004 Volvo S80:
* 2.5L 5-cylinder engine: This was the base engine option, producing around 168 horsepower.
* 2.9L 6-cylinder engine: This engine was available in the S80 T6 trim and produced around 268 horsepower.
* 4.4L V8 engine: This powerful engine was available in the S80 R trim and produced around 300 horsepower.
Please tell me the trim level of your 2004 Volvo S80 (e.g., S80, S80 T6, S80 R), and I can tell you the exact engine size.