No car "needs" a 4-wheel alignment if the rear (IRS) isn't wearing the tires unevenly it hasn't been "tweeked" in an accident, and a friend following your car doesn't report that it is going straight down the road "doggie style" (car not aligned with direction of travel). IMHO I think a lot of shops screw up rear alignment (there are notable exceptions), so if it ain't broke, don't fix it.

Personally, if the above parameters are OK, I would just have the front rubber bushings checked (since those do affect alignment) and have the toe set properly. If they do it right, your steering wheel will be centered (someone recently posted that post-alignment, theirs was off) and your front tires will wear perfectly.

As for my basis for these statements, my dad operated an alignment shop for 30+ years (and I spent too much of my youth there soaking up practical knowledge).

If you have a 940 or 940 turbo then you don't.
If you have a 940SE sedan, or a 960 sedan, then you do, because you've got
independent rear suspension. The wagon versions of these cars, these
years, got a solid axle and therefore don't need a 4-wheel alignment.
The late 960 and V90 wagons do have independent rear axles. 1996 on.
--
Rob Bareiss, New London CT ::: 86 244DL, 87 244DL, 88 744GLE: 625K total

You need a four wheel alignment only if you have independent rear suspension. Your car most likely has a solid rear axle and thus does not need the rear settings changed.

However, you do need t make sure the thrust alignment is correct, measuring front to back, so they may charge you for a four-wheel alignment.