Volvo leans heavily on its Swedish roots and builds strong machines that can withstand the harsh winters in its home country. The Scandinavian carmaker was launched almost a century ago and has made a name for itself as a bastion of car safety. After all, it was Volvo engineer Nils Bohlin who refined the three-point safety belt and shared the patent with the rest of the industry. With the 2025 XC90, the largest SUV in Volvo’s line-up, the brand has raised the bar even higher with a new version.
After twenty years, the XC90 is only in its second generation, which could be a sign of an outdated, tired model. However, Volvo has a few new tricks to keep the three-row SUV current, and this model year includes significant upgrades to the technology, standard suspension system and powertrain.
Everyone’s talking about the sub-$40,000 Volvo EX30 EV, but the XC90 is far from over. The 2025 model makes it look more like its all-electric EX90 sibling, bringing the family closer together. Additionally, the 2025
Miller Cycle increases fuel efficiency
When it comes to modern engine history, we have to go way back to 1876, when German engineer Nicolaus Otto found a way to harness air induction and combustion to create power through compression. British engineer James Atkinson improved on this idea in 1882 with his four-stroke design, using a shorter and more efficient compression stroke.
Decades later, Ralph Miller patented the Miller cycle engine in 1957 for even greater efficiency. The simple genius behind the Miller cycle is that it leaves the intake valve open during part of the compression stroke. As a result, the engine squeezes against the pressure of the supercharger instead of against the cylinder walls.
Volvo powertrain engineer Stefan Molen says that while the supercharger in the 2025 Volvo XC90 B5 and B6 models is not new, the addition of the Miller cycle makes it more efficient. “Updating the engine with the Miller cycle results in a four percent reduction in fuel consumption, which is quite a bit,” he says.
“The trick [of the Miller cycle] ensures that the intake valve remains open even longer and compensates for compression losses by using forced induction,” MotorLabs say. “By allowing the compression stroke of the rising piston to push air back into the intake manifold, the cylinder itself never reaches maximum capacity, but pumping losses are also reduced.”
While this design can lower performance figures at lower speeds, the statement continues, ignition efficiency increases significantly when that piston begins to descend. The result is a shorter intake stroke with less force and a full downward “power stroke” for an improved compression process.
For the 2025 B5 model, for example, that translates to a two-mpg improvement over 2024.
Frequency selective damping, explained
Ride comfort in the XC90 was never a low point. For 2025, the automaker has gone a step further with new standard suspension in the B5 and B6 gas-only trim levels, using Frequency Selective Damping technology.
“We took the standard suspension and raised it to the next level,” says Volvo vehicle dynamics engineer Alessio Violin. “We basically delivered a new suspension tuning package, including the springs, dampers and anti-roll bars, and adjusted the steering boost curve to match the response of the tires.”
By integrating an additional valve into the shock absorbers, the system regulates parallel oil flow in addition to the primary flow through the piston assembly. When the valve stops the parallel flow, the damping forces increase in correlation with the duration of the unidirectional movement of the piston on the rebound side. By adjusting the rest of the suspension system, Volvo wants passengers to experience a smooth and balanced ride.
“The FSD valve makes the car more predictable and ensures a high level of comfort,” says Violin. “FSD provides freer wheels, which reduces vibrations in the seats.”
The “frequency” part of FSD isn’t a frequency you can hear, Violin says. it is a low frequency that affects the vehicle feel on the road.
“Say you go over a little bump,” Violin explains. “Basically on the compression side it doesn’t do much, but on the rebound side it sinks a little faster and travels further away from the body. Over a series of small bumps, the wheels follow the texture of the road.”
Driving over the nearly 10-mile long Øresund Bridge between Denmark and Sweden, I noticed the difference in the gasoline-only model. However, if that’s not smooth enough for you, the plug-in hybrid is available with an even better air suspension, but you’ll pay a premium: the XC90 T8 starts at $73,000.
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