Found on this page Real Volvo fuel consumption | Auto ABC (auto-abc.eu) that for newer XC models (up to 10 years old) real consumption is about 30% higher than official.
For older Volvos difference is much smaller or even no difference. What's your experience?

 

first you need to understand what "official" really means here. New cars in the US go through a prescribed driving cycle to produce a city and highway estimate to use for comparisons between makes/models. The window sticker clearly says your actualy mileage will vary. Reason is pretty simple - you are not driving a fixed driving cycle and there are seasonal variances as well. I typically find I get up to 2 less MPG city in the winter vs summer. Why? Cold starts, winter blend fuel formulas, cold tires etc. I also can see my highway mileage vary 3-4 MPGs. average road speed variances, aggressive vs passive driving, flat vs hilly terrain can all add up. Biggest factor in mpgs is always going to be your driving style, city vs highway mix and top speed. Can't blame Volvo for any variances vs sticker, its the same for all cars.

 

Yes, but that doesn't explain why the official consumption figures for older cars are more in line with the real ones. In fact, "official" fuel consumption should be renamed "lowest possible" fuel consumption, at least nowadays

 

curious who came up with the 30% differential number? Have you found any road tests (like from Car and Driver or Road and Track) that talk to what their experience was during testing? I've never owned an XC90 but our 1995 850T typically would get 20-21 in town during the summer and 18-19 in the winter and 27-28 highway (70-75 speeds). Car was rated at 19/26. Our 2000 S40 typically gets 22 in town, 26 highway, car is rated at 21/28. My 2012 VW CC gets 22-23 in town, 31-33 highway, rated at 22/31. Note that my in town driving is not real NYC stop light to stop light stuff more stop signs, a few lights and half mile road stretches. Full mid town city driving will take 2-3 MPG off any car...

 

Also think of all the new cars that use start/stop to reduce fuel consumption, which is a feature that benefits most from longer stops, like city driving. And then think of all the people, like myself, that turn it off because it is annoying. My car is rated 22 city and 30 highway. My highway is more congested and my "city" is like my6127's. I get 25mpg average with my car, so i would say I am right on target given I drive 50/50 based on miles.

 

Doesn't matter the brand forum, this is a nearly universal post. The important things to remember is that manufacturers have an significant interest in having the milage figures as high as possible and the government is seldom honest and even less frequently competent. The end results are that the published data reflects what various people, departments, and agencies want. What we, as consumers want, really doesn't matter to any of them. The best you can hope for is to use them for comparison between competing cars - such as " I want a mid size, semi - luxury SUV - how does the milage compare between an XC90, an MDX, and an X5". All figures will have been "fudged", but pretty much in like manners so you can at least see where each car falls "in class".

And don't forget, they test with pristine new plugs, clean throttle bodies, new air filters, empty trunks, and so on. I never change everything all at once every 20,000 miles. I also haul a bit more stuff than I need to (but less that I did in the '70's when I lugged around 2 tool boxes, several gallons of antifreeze, a few quarts of oil etc.)

But, in response to your statement that "older" volvos are more in line with stated ranges, I started out in 1998 with a '98 S-70, it was significantly less than the sticker stated. And so have all my subsequent Volvos. And despite what I said above, I blame neither Volvo nor Washington - the fault lies with the fact that there is significantly wide amount of potential throttle travel but I tend to use the higher ranges more than those testers.
Great mileage? No.
Get where I'm going faster? Yes
Have more fun getting there? Yes

And of course, 2 outta 3 ain't bad.