On our 2000 S70 2.4 with a T5 (high pressure) turbo, we typically got
30-31 MPG highway and around 24MPG in town, 2 people in the car, with
about 26 MPG in mixed usage. Since the turbo usually kicked in in
stop-and-go traffic (rather than highway which was usually just
coasting), I'd think you'd get better than that in mixed conditions
without a turbo. Overall, 22.5 seems kinda low.
I still have the Volvo card provided with the handbook, which has the
mpg figures for all the range. The figures for the 2.4 20v NA model with
auto are:
18.0mpg Urban (Cold)
35.8mpg Extra Urban
26.2mpg Combined
The 10v version is about the same, just slightly worse at speed and
slightly better urban. I know these figures aren't especially
optimistic, because my T5 manual averages 26 doing runs that are mixed
but mostly urban, whereas the combined figure quoted on the card for it
is 25.
Of course, these figures only apply to the 1997 model year, which means
cars built with the old Motronic 4.4 fuel system. Later models had ME7,
which includes distributorless ignition via separate coils and a fly-by-
wire throttle. Therefore, newer ones may be slightly more efficient.
In short, the OPs 22.5 does seem rather low, assuming that he is doing
genuinely mixed driving.
Stu