philmk

I recently purchased a 2012 with a 3.7 L and about 70k miles. I am only getting 12 - 13 in town and about 17 MPG on the highway. I truly do not think it is my driving as I have been attempting to baby it lately and it doesn't seem to help. Highway driving is done at 70 MPH. I also find the truck to be pretty sluggish when I do try to get on it. I swapped out the spark plugs recently (they appeared to be a little worn) and that didn't seem to do anything. Any thoughts on causes or where I should turn next?

Thanks,
Phillip

SALEEN961

iTrader: (1)

I would check your air filter, on my 5.0 replacing one that didn't even look that dirty made a surprisingly large difference. Filling up at better gas stations like Sunoco and BP has also consistently given me an extra 1-2mpg across many vehicles.

Since you just got the truck I would also check your tires, tire pressure can make a big difference, but if the type or size of tire doesn't match the sticker in your drivers door jamb you may find that you're getting better mileage than you thought, or find that the tires are the reason for your poor fuel economy.

brihvac

Sounds about right.
People are always under the impression that a smaller motor will get a lot better mileage and it is simply not true, The reason is that the smaller motor has to work harder to push that heavy truck which equals using more fuel. A larger motor uses less effort which uses less fuel. I get the same mileage as you with my 5.0 on the highway. Around town I get better (14-15) because my 5.0 has to work less to push my truck stop and go. Boats really see this issue when under powered. As far as being sluggish....its a 6cyl without a turbo. Its not going to accelerate like a V8 or Ecoboost. Also are you 4wd? What rear ratio? What you are describing sounds normal to me. But still check what SALEEN961 outlined; you might be able to squeeze a hair more out of it. Never believe those numbers on the window stickers. I have not had a vehicle yet that has gotten close to those numbers.

doolyd

I have a 2013 FX4 4 door 3.5 ecoboost, leveled, 3.55 rear and about the same mileage 62K. I get the same MPG. I have monitored mine since new.

I did notice that my mpg seemed to have dropped around 40K. I was consistently getting 17-18 highway mpg and that dropped to 15-16.

My rotors were warped and were replaced along with new pads. Immediately after doing this and new tires I got back to 17-18 but it dropped again in about a month.

I just cleaned my mass airflow sensors, there are three on ecoboost, and again my mileage is back to 17-18 highway. It has only been a week so don't know if it will stay like this. Little irritated by this since it isn't in the book as any type of maintenance item.

I plan on doing my spark plugs in the next couple of days just waiting on Amazon which should get here today.

I would also suggest doing the Adaptive Memory reset procedure since you mentioned you recently bought it. I would do it when you clean the sensors.

There are youtube videos for all of this.

So my suggestion would be to check what I have mentioned above but I am fighting just to get back to a consistent 17-18 highway mpg. Neither my route nor my driving style has changed so I am at a loss and I would consider yourself lucky you get mpg that good. I remember when I first got my truck and only drove 10 miles to the park and ride I was getting 12-13 mpg and people said it gets better when broken in. Well that never really happened. City driving I still get 13-15 mpg if you want to call that an improvement.

jhanna

I tend to agree with checking tire size . I also have a 2012, 3.7v6, 69,000 miles, stx regular cab

I get 22 mpg hiway, 19-20 around town, and I have confirmed it with a gps and pad/pencil.

My stock tire size was 235/75/17, but I changed to 255/70/17. A little wider but same height so odometer and speedometer are still correct.

And I'm still running original spark plugs.

Doolyd, Yes, God bless Texas, but the rest of the USA needs it too.

philmk

Thanks for the replies. I have read many other threads who mostly indicate to get mileage to what 2jhanna is getting. 22 hwy and 19-20 in town.

I am running a 2wd extended cab and the factory size tires based on the door sticker, 265/60/R18. I'm not sure of the gear ratio.

Sticker calls for 35 psi. Any thoughts on bumping that up to 40 or 45. I don't want to go too high to affect tire wear. I'm just not sure how high is too high.

jhanna

I can't say specifically (I don't have factory tow option), but are you using all 6 speeds on the tranny. I think the towing option gives you the choice of locking out top speeds.

Maybe someone else will chime in.

This wouldn't explain the sluggish though.

Blondie70

My 3.7 is getting 20-21 on the highway at 72.5 mph. Lots of pep and I am very happy with it. Using all 6 gears too...ha ha ha Radio works too.

Spiky

You can lock out gears anytime with the +\- button on the shifter, not the tow button.

jhanna

I was referring to the optional factory tow package. My truck does not have the option, therefore does not have the +/- lock out button.