MPG Drop after maintenance for check engine light

Last week we took our 2001 Subaru Outback H6 in to find out why the check engine light was on.

The Independent shop I took it to claimed that the code was for a “bad battery”. No battery, terminals installed and the “check engine” light went out.

Now the fuel economy has dipped by at least 5mpg.

The repair people say they did nothing to cause this.

Anybody have any thoughts about this six cyclinder Subaru??



Duplicate post. Responses posted to other original message.