XC90 T6 AWD drastic reduction in MPG

[mgjonesin]

Thanks in advance for any input.

Car use to get 18 MPG per the computer. Dropped to 14.5 recently so I changed the O2 sensors. This had no effect on the MPG. Next I cleaned the mass air sensor with CRC MAS cleaner. That screwed up the sensor, so I replaced it. Now the car is getting 10 MPG!

Where to next? Dealership for ECM reboot?

Thanks again,

Jon

[hoonk]

Where to next?

Get an accurate reading - Measure the actual gas mileage - fill tank, reset odometer, drive x miles, refill, repeat several times. Then determine how much (more) you want to spend in an attempt to get better mpg. Summer blend gas is supposed to get better gas mileage - so when it is sold in your area watch out for the change in MPG with that.

If your mileage actually went from 18 to 10 - the engine could be running rich and would set fuel trim codes - Have you checked the fuel trim readings?

What o2 sensors and air mass meter did you use? - (oem or aftermarket) I trust you replaced the front ones.

"Reboot" the ecu by disconnecting the battery holding the terminals together for a few minutes.

[mgjonesin]

Thanks hoonk,

I used Bosch O2 sensors for all 3. The rear was a universal.
The MAS was a rebuild from NAPA and it's running without the surges it had before.
I'll have a friend check the fuel trim, my scanner doesn't do that.
I'll get an accurate MPG reading and reset the ECM.

Thanks again

Jon