We recently took our 2013 XC90 to the local Volvo dealership and were informed we needed a TCM software upgrade that was done.

We have had the car back for less than two weeks and of are now getting 25% less mileage than previously. Can this be a result of the software that was installed not working properly?

 

You went from 20 to 15 mpg? Is this the readout on the dash or have you filled the car, driven x miles, filled it again and calculated the real mpg?

Does the transmission shift normally?

 

Actually long distance (highway driving) we had over 25 MPG, we could drive from Columbia, SC to Daytona Beach, FL and have 1/4 tank of gas. Now if we drive to Jacksonville,FL we have to stop to get gas. Short answer is we went from 25 MPG to less than 20 MPG.

Transmission seems to shift normally. The dealership stated it takes the software some time to “normalize”.

 

We filled the tank, drove the miles and refilled the tank so the calculation for MPG was manual.