Aye dude! You went all American on us.
1 US gallon is 3.43 litres.. (I believe the Yanks like to show off what shocking consumption their v8s manage).. whereas a "proper" gallon is 4.54 litres.
So as djstanley says, you're actually hitting 21.72mpg. That's not far off normal... thought it depends how much idling in traffic your missus is doing.
On a main road run the beast should be returning about 28mpg - 30mpg... so check that the temperature climbs up to 88C regardless of the whether the car is moving or not.. and stays there. If it's loitering around the 75C mark when moving, then the thermostat is shot and that's 3-4mpg right there.
Thermostat is easy to get hold of and change..
While you're at it.. I guess it's a bit nippy out there now.. make sure your oil is 10W40 and not a heavier grade..
Cam-belt.. you got me all metrificated again..
but yes.. the regular cam-belt change interval is 72,000 miles (120,000 of your klickometers).
My old belts have never appeared even vaguely distressed or "worn out" when I've removed them and they have been in there 72k (120k) and for 4 or 5 years... when hearsay would suggest they should be dry and cracked and falling apart. They don't die.. but have a peek at yours every now and again... environment and use might be a factor.
The cam-belt tensioner is some left-over old stock that was originally intended for a battleship. It's pretty indestructible and will easily cope with 72k (120k).. but 2 Tours of Duty brings them right to their limit (my old one was veeeery loose after 200,000kms in there..
Don't worry about the water pump.. My old beast did more than 300,000kms and was still pretty good when I took it out, since it just *had* to be knackered. It wasn't.