I have a MY01 Subaru WRX ipmreza.

The fuel usage has increased by approx 40-50%. I am still using the same fuel and the same route.

I have delta dash software. Is there anything I can check before i take it in to the garage . It has done approx 49000 km. Unfortunately I do not have a before run.

 

My guess would be a dodgy lambda sensor, so to check it you'd need to compare the reading from a WOT run when it was doing OK to what it's doing now (as at WOT it's not checking the lambda you'll get an actual reading rather than an adjusted reading!)
That's my guess, anyway

 

Do you have an idea of the range of a properly functioning Lambda sensor? I assume it would have to be in volts.

TIA

 

It fluctuates between 0 & 1v, but aside from that, I think you'd need the answer from another MY01 owner - I believe the numbers are different on them to a classic? (I have a classic )