Volvo claims the V8 offers competitive fuel economy with the out-going XC90 T6 model. Which is really damning with faint praise. The T6 was a pig on gas. Frankly, I didnt find the V-8 to be any great shakes on fuel economy either. I got just over 11.5 mpg in mostly city type, short hops. Regardless, 11.5 mpg is simply not a sustainable number these days for any personal vehicle. EPA numbers are 15 city and 21 highway.
Every XC90 comes standard with roll stability control (RSC). The system uses gyroscopic sensors to register the vehicles roll speed and angle. Using this information, the terminal angle is instantly calculated and, with it, the rollover risk. If the calculated angle is greater than 13 degrees and there is a clear risk of rolling over, the DSTC (Dynamic Stability and Traction Control) anti-skid system is activated to put things to right.