My 1995 Corolla just had a new clutch and struts put on. They noticed a lot of wear and tear as expected. But now it eats through gas like a fire burning through an oil spill... Any reasons why this might be? Went through complete tank in less than 2 days: a tank normally lasts 1-2 weeks with the limited driving I do!
My first thought is dragging brakes. If that's happening you should notice that one or more of the wheels is quite warm after driving for even a short (1-2 miles) distance.
With a problem that comes on shortly after having work done on the car it would be very reasonable to take the car back to the mechanic and ask them to double check their work.
This is an enormous increase in fuel consumption, don't know if it is possible for the engine to burn that much more fuel under any circumstances. First place I would look is for fuel to be leaking on the ground, could they have damaged a fuel line or connection when they changed the struts and clutch. If it's a leak, might only happen when car is running, so you would not notice this unless carefully checked out with engine running.