The owner's manual says... for optimum performance use Permium (91 octane). The engine is set up for peak performance with this octane rating. My S60 2.4T will get 1-3 MPG better with Permium (91) than with Regular (87) . During the $4/gallon gas prices, I dropped the octane rating I was using, and saw the mpg drop. But I am back to using premium after calculating I wasn't saving any money The owner's manual also says that you should not use less tha 87 octane.
The 2012 Volvo S60 runs on regular unleaded.
The 2013 Volvo S60 runs on regular unleaded.
The 2015 Volvo S60 runs on regular unleaded.
The 2014 Volvo S60 runs on regular unleaded.
The 2011 Volvo S60 runs on regular unleaded.
The 2005 Volvo S60 runs on premium unleaded (required).
The 2009 Volvo S60 runs on premium unleaded (recommended).
The 2004 Volvo S60 runs on premium unleaded (required).
The 2003 Volvo S60 runs on premium unleaded (required).
The 2007 Volvo S60 runs on premium unleaded (required).
The 2001 Volvo S60 runs on premium unleaded (required).
The 2006 Volvo S60 runs on premium unleaded (required).