Fuel Economy Decreasing

[FordandPolaris]

So I have noticed recently that my fuel efficiency is going the wrong way. Used to get around 11 mpg's through the city, but the last few months it has been more in the high 8 low 9's. I am slowly changing out spark plugs and COP's as they go bad, but otherwise the truck runs just fine. I am wondering if bad O2 sensors could cause this? They have been throwing a code for like a year now, but they have been low on the priority list of things to repair. Also the codes came up long before my fuel efficiency issue. If anyone else has ideas on what could cause a decrease in mpg's I would appreciate the advice, thank in advance!

 

[toms89]

Yes bad O2 sensor(s) can cause a loss in fuel economy. If the pcm has determined they have failed or reading incorrectly it will stay in open loop and its programmed to run rich to be on the safe side.

As O2 sensors go bad they become less responsive and I believe they generally read lean which will cause the pcm to compensate by adding fuel.

 

[FordandPolaris]

Alright thanks tom, I will go ahead and replace them when I have time and it gets a little warmer...

 

[1997SCEBFEX]

Yes bad O2 sensor(s) can cause a loss in fuel economy. If the pcm has determined they have failed or reading incorrectly it will stay in open loop and its programmed to run rich to be on the safe side.

As O2 sensors go bad they become less responsive and I believe they generally read lean which will cause the pcm to compensate by adding fuel.

+1 on this. would also inquire as to where you purchase fuel, same or varied locations/dealers, and if you use any additives etc due to the E10 issues. these could contribute too, but as Tom said, the 02 sensors will def contribute to decreased mpg.

 

[Whack]

+1 on the O2 sensor stuff...


Saint Cloud, MN?

How cold is it getting there? Are they using a crazy winter mix gas?

Sometimes the winter mix can lower MPG, and the colder it gets the weirder it seems to be.

 

[whowey]

Winter fuel. I've lost almost 6/10ths off my last MPG check due to the winter fuel blends.

 

[DF5.4]

This time of the year is not good to MPG

 

[FordandPolaris]

Yeah I have lost 2 mpg's since the summer. Seems a lot to blame on winter blend alone. Also I buy gas a varying locations. Its been cold though haha. Woke up on tuesday to go to work and it was -17. The truck surprisingly started, but the gear shift was all stiff cause of the cold. I will start with the O2's.

 

[flyin]

When it is very cold nothing wants to move or turn. Gear oil and grease resist movement. Try pushing a cold vehicle. They don't want to move. Not to mention warm up time.

 

[toms89]

When it is very cold nothing wants to move or turn. Gear oil and grease resist movement. Try pushing a cold vehicle. They don't want to move. Not to mention warm up time.

Mine does. Seems like the motor wants to jump out of the engine bay soon as I tip into the throttle. Loves the cold dry air!!! (high air density)

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