Lowered fuel efficiency after accident and repairs?

My 2014 Subaru Forester was rear ended when it was all of 3 months off the lot. After about $6k in repairs to mainly the bumper and lift gate, plus some “pulling” of the rear quarter panel, it has not achieved the fuel efficiency I had pre-accident. It is rated 24 mpg city and 32 mpg highway (27 mpg combined), and before the accident I was averaging about 28-29 mpg combined and often achieved 32 mpg on highway trips. Now, I’m around 18 mpg city, 27 highway. I took it to Subaru to see if they could figure anything out that was related to the accident and repairs, and they found nothing wrong with it.

Does anyone have any ideas what this might be related to?

Have you noticed any reduction in power?
Is the tranny shifting onto overdrive?
Have you had any Check Engine Lights?

Damage to the exhaust system causing a restriction,
damage to a component that provides a fuel metering input to the ECU,
damage to the induction system causing restriction,
damage that affects the ability of the tranny to access overdrive,
damage to a brake component causing drag,
damage to the AWD fluid coupling system,
all and more are possibilities.

The first thing I’d look at is the brakes, because they’re critical. An infrared thermometer can measure the wheel temperatures at the hub and tell you if you have one dragging. Don’t forget too that a misadjusted parking brake can drag, reducing mileage. If the rear quarter had to be aligned on an alignment machine, it’s very possible that serious brake work was done in that area.

Bearing damage is another possibility. Has anyone checked the wheel bearings?

Post back. We do care.

How are you figuring the fuel mileage? By working the math on miles driven vs gallons to fill or by the dashboard gauge, etc?