20-30% mpg loss..

Hi all!

Longtime reader (which I can’t state how much you guys have guided me through A LOT of tune up work.. thx!) & first time commenting ( ;

My 2010 V6 4WD has 90k miles.

Last month I started losing 20-30% mpg.

As we know there’s some mpg loss when winter sets in. Though not to this extent.

When the scheduled 5k mile maintenance light kicked on ~ that time I fooled myself thinking an oil change was the cause.

I changed the oil (high mileage synthetic), oil & air filter, greased the driveshaft, cleaned the mass airflow sensor & throttle body.

No change in poorer mileage.

Last month I’d also gotten my 2 yr. old new recalled frame (though not needed I couldn’t pass up a new frame/ nuts & bolts/ brake lines) professionally coated. Including the gel packs.

I though maybe the O2 sensor’s internals were exposed & possibly affected by the coating. Nope.

The maintenance light hasn’t turned on since resetting it post-oil change so I’m at a loss.. in more ways than 1!

Hoping you boys can help me before bringing her to a shop.

Thanks in advance, have a wonderful Christmas, Hanukkah & New Years ( :

P.S. pics to follow.

 

Ok well first off, the maintenance light is triggered only by distance traveled. Therefore, if you don't reset the maintenance light even after you changed oil, the light will stay on. It's possible that the maintenance light intervals will be off sequence of when you actually changed oil so be sure to reset the light after maintenance.

Second, there are numerous factors that will affect gas mileage. It could be internal or especially external by way of the environment. How are your tires? Have you been driving into constant head winds? What about the load you're carrying? Has that changed?

 

Can you hear any exhaust leaks in the cab?

 

Winter fuel blend will drop you at least a couple % mpg.
Checked your tire pressures?
Warming the truck up more than necessary?

 

I’ll say buy new shocks and change the rear diff oil to synthetic.

 

Wow, the quick responses are MUCH appreciated.

1) Tire’s tread & inflation numbers were & are good.

2) Haven’t towed anything the past couple months & the weather, winds have been very mild so no need to warm the truck for too long prior to driving. Though I tend to let it idle for 30 or so seconds when starting it, regardless of year. Even when in the garage. The temps have been between the low 20’s though 40’s - low 50’s the past couple weeks.

3) I changed the front & rear diff at ~ 88k. I planned on changing the transfer case at 95k per the maintenance log. I can do that sooner though. Haven’t used synthetic but will try that as well.

4) Haven’t changed the shocks yet. Though am game if that tends to be a problem &/ or possibility of improving mileage.

5) No exhaust leaks in the cab, either. She purrs quite nicely.

 

Clean the maf sensor, too and tighten all the intake hoses. Replace those dry rotted vacuum lines while you’re at it.

 

Yep, cleaned the maf sensor.

 

Do you have a scan tool or way to read codes/data?

Look at the long term fuel trim and see if it's high while driving around

 

1 of my buddies has a scan tool.

I’ll check the intakes again as well.

 

You're not alone. I've been getting 17 MPG lately when I can get 22-24 on the same trip in the summer. For me, I think it's a lot to do with weather conditions in addition to winter gas. It hasn't been very cold here (32 or below) and has been very humid and damp.

That being said, is it possible you hit a pothole or something that would knock your alignment out of whack? That would cause an MPG hit even if you don't notice any direct symptoms right away.

 

Hi RedWings44

I haven’t noticed any drastic pull when driving. Though it’s been a tad less than a month there hasn’t been any noticeable uneven tire wear.

Though have been meaning to look at the alignment too.

Thanks for the tip.

I’m going to be busy this Christmas break ( ;

 

if you ask me,

-replace O2 sensors with good quality
-synthetic oil. Not "high mileage" oil
-replace Tstat
-verify spark plug condition
-clean TB and MAF as needed
-verify brakes operating properly and not dragging

most of which already did

 

Fuel trims will help you cut your diagnosis in half.

If the trims are high, then it's a calculation issue. The pcm is seeing something it doesn't like and is adding extra fuel on purpose. Anything from a exhaust leak, poor fuel quality or a faulty sensor can drive the system rich.

If the fuel trims are low or close to zero then that means the computer has good control and the mixture is correct pretty much all the time. That would mean you're looking for a more mechanical issue like tire weight, dragging brakes, too much skinny pedal, etc

 

Recharge the flux capacitor?

 

You guys rock.

Btw my flux capacitor is always operable with spare uranium in the bed.

 

How are you calculating milage and any change in tire size?

 

point45 - Calculating mileage via the odometer.

I’ve a gas can. Drove it til empty in the sticks to be sure the odometer was operating properly.

The tires are the same size, holding the proper amount of air.

 

The throttle body like stated above is an easy thing to clean. Just so happened I cleaned my F150s TB this afternoon