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As many of us do, I track my fuel mileage closely. I’ve noticed about a 5 mpg decrease in fuel economy during my commute lately. I’m struggling to get my 25 mile average into the 50’s, when mid-50’s was the norm over the same stretch of highway. First I attributed it to “winter fuel” and colder temps. But I noticed something today that makes me think there is an issue with my car.
Typically my Economy Trend page has all segments lit up with 50+ mpg trends. I have been seeing this sawtooth pattern over the past few weeks and today it hit me.
Seeing the repeated pattern every 3 miles made me think something in my computer is resetting on a regular interval. I started going over items that could cause this. The first thing I thought was fuel trims getting out of whack by an air leak and resetting. But I haven’t noticed any driveability issues or abnormal idle.
With the holidays, the car has been sitting for days at a time. I noticed that if it sat for two days it would crank real slow, so I have been keeping a battery tender on it to keep the battery up. I finally put two-and-two together and seen the battery voltage sticking at 15.0 volts during cruise, it is usually 12.2 volts. I believe the battery being weak is putting a higher workload on the alternator causing the fuel mileage to cycle the way it is.
Have any other Eco owners seen a similar trend?
Typically my Economy Trend page has all segments lit up with 50+ mpg trends. I have been seeing this sawtooth pattern over the past few weeks and today it hit me.
Seeing the repeated pattern every 3 miles made me think something in my computer is resetting on a regular interval. I started going over items that could cause this. The first thing I thought was fuel trims getting out of whack by an air leak and resetting. But I haven’t noticed any driveability issues or abnormal idle.
With the holidays, the car has been sitting for days at a time. I noticed that if it sat for two days it would crank real slow, so I have been keeping a battery tender on it to keep the battery up. I finally put two-and-two together and seen the battery voltage sticking at 15.0 volts during cruise, it is usually 12.2 volts. I believe the battery being weak is putting a higher workload on the alternator causing the fuel mileage to cycle the way it is.
Have any other Eco owners seen a similar trend?
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