I work at an independent Volvo shop, almost every newer one that comes in looks like that under the filler cap/dipstick...even the ones that are serviced by the book. The problem is the long recommended oil change interval, which is every 7500 miles on conventional oil (even for turbo models). It's hard to convince people to change it sooner, because they think they are already doing good by following what Volvo says to do. The customers that use synthetic or do an "in-between" oil change with conventional typically don't have the buildup under the cap.