Poor gas mileage

[Coronado]

Recently purchased a 2012 Ford Edge Limited AWD 3.5L with 155K miles.

 

Engine and transmission seam to be strong with no signs of problems. However, I can't seam to get anything better than 12mpg regardless of driving style.

 

Just did an alignment, and oil change. No change.

 

I've read that spark plugs and fuel filter might be a root cause to bad mpg. True or false?

What other things should I look into to resolve this?

 

Thanks for any feedback.

[MLTEdge]

Yes, plugs, wires, fuel filter, injectors, gas, water in tank, tire pressure, compression loss, dragging brake, age, prior owner messing with vehicle or chip, kids syphoning, towing an elephant...  Many things can cause poor mpg.  Bad mpg can be difficult to nail down without a full vehicle diagnostic. Rarely is it something simple though unless only off by 1-2 mpg.

 

On a funnier side.... My sister a few years ago bought a c class Mercedes. She took it to dealer 2 or three times over several weeks complaining the mpg was too good, or the gauge was broken. She'd never filled it and drove 900 miles . Turned out her husband was dumping extra gas for his generator in the car so he could store a fresh supply. A good laugh... For everyone but my sister.

[DILLARD000]

On 9/14/2022 at 6:57 PM, Coronado said:

...2012 Ford Edge Limited AWD 3.5L with 155K miles.

...no signs of problems

...read that spark plugs and fuel filter might be a root cause to bad mpg.

...other things should I look into to resolve this?

At 155kMiles, if OxSensors are factory originals, theyre ~55kMiles overdue; will defintely cause bad MPGs as they age.

That along with new Plugs should be done every 100kMiles.

On a new-to-you 10yo car, change all fluids: Oil+Filter, ATF, Coolant, PTU+Dif GearOil..., syphon+refresh Steering & Brake reservoirs several times.

Be aware of the notorious PTU in the AWD models, so get that GearOil changed every 33kMiles.

InternalChainDriven WaterPump in these 3.5\3.7L engines is also a NotoriousFailureItem & expensive fix at that;

consider pre-empting that failure & get that changed before it craters & destroys engine.

 

Edited September 20, 2022 by DILLARD000

[Coronado]

Thanks for the feedback.

 

Since my original post, I had a new water pump installed from NAPA. So orange coolant has been replaced as well.

 

Unknown if last owner did any of the other suggestions.

So I guess next on my list will be...

OxSensors / Plugs / Fuel filter

Then...

ATF / PTU+Dif GearOil / Steering & Brake line flush

 

Thank you again.

[WWWPerfA_ZN0W]

prob stupid question, but have you reset the mpg since you got it?

 

do you drive primarily in the city or heavy traffic?

 

new plugs will be a nice boost if the installed plugs are original to the car.  motorcraft plugs are your best bet. you can find the coils in a pack from an online ford dealer ba5z12259a. the gaskets and plugs will not fit your MY tho. ford keeps raising the price, but still better than paying for them individually.

 

definitely assess the health of the ptu and rdu.

 

hopefully you had new chains and tensioners installed with the water pump, bonus if you did the vct solenoids as well.

[Coronado]

On 9/24/2022 at 1:07 AM, WWWPerfA_ZN0W said:

prob stupid question, but have you reset the mpg since you got it?

 

do you drive primarily in the city or heavy traffic?

 

new plugs will be a nice boost if the installed plugs are original to the car.  motorcraft plugs are your best bet. you can find the coils in a pack from an online ford dealer ba5z12259a. the gaskets and plugs will not fit your MY tho. ford keeps raising the price, but still better than paying for them individually.

 

definitely assess the health of the ptu and rdu.

 

hopefully you had new chains and tensioners installed with the water pump, bonus if you did the vct solenoids as well.

 

Yes. MGP onboard computer was reset. Driving.... 60% city, 40% highway.

Just installed motorcraft plugs and coils.

RDU gear oil has been changed.

PTU still needs to be checked.

Water pump only replaced.

 

Still getting 11 mpg average.

 

I read a few posts about mass air flow sensor. They claim that if unplugged, idling car will shut off. If car stays idling, then the sensor is bad. Is this true?

I unplugged mine and car continues to idle. Time to replace?

 

[Coronado]

Update:

Replaced the mass air flow sensor, and after about a week of driving around, I retested the MPG again, Now seeing an average of 13.8 MPG with 40% highway / 60% city driving.

 

So I guess headed in the right direction, but still shy of what I believe should be the average MPG of around 19.

[WWWPerfA_ZN0W]

unplugged the car will continue to idle but it will set a code. you can drive with it but it will be rough and have loss of power. with lack of input from the MAF, that is what you will experience.

[DILLARD000]

If OxSensors are 10yrs\100kMiles+, they read lean & thus bias the Air+Fuel mix too rich, causing MPGs to drop & CatCons to run hot.

So be sure to get those renewed if needed; read live OxSensor data via OBD2 to confirm their signals are in the acceptable\normal range.

[Coronado]

17 hours ago, WWWPerfA_ZN0W said:

unplugged the car will continue to idle but it will set a code. you can drive with it but it will be rough and have loss of power. with lack of input from the MAF, that is what you will experience.

 

Thanks for the feedback!

[Coronado]

4 hours ago, DILLARD000 said:

If OxSensors are 10yrs\100kMiles+, they read lean & thus bias the Air+Fuel mix too rich, causing MPGs to drop & CatCons to run hot.

So be sure to get those renewed if needed; read live OxSensor data via OBD2 to confirm their signals are in the acceptable\normal range.

 

Good to know. I'll be sure to check out what the values are and see if within range. Thank you!