Horrible Fuel Mileage!!

[Dirty_Stroke]

Alright guys I need some opinions here. I usually run the Looney Wild on trips because it has gave me the best mpg's in the past. Yesterday I came down to the beach and it's about 5 and half hour trip so I swapped to the looney and filled the truck to the rim. I noticed about half way down here that it wasn't getting near as good mileage as usual. When I got here I refilled the truck and it confirmed it.... 13.6mpg My truck usually gets that or better around town, and 18-19mpg on the highway! I took a trip about two months ago and running 78-80mph I got hand calculated 18.6mpg. The only thing that has changed since then is I put new tires on it. They are the same brand and size and have 65psi in them so I don't think they are what made me lose 5mpg! Also I was running slower on this trip so I can't see why it wasn't better mpg. I did notice my oil cooler is clogged cause it's hovering around the 13-16 degree difference, could that cause bad mileage?? Sorry for the long post but I just feel something is wrong for it to lose that much mileage. Could my FICM voltage be low and causing it? I'm just looking for replies for things to check when I get home.

[jesilvas]

Sticking brake calipers, EBP sensor maybe.

[colo_dually]

If you haven't checked, I would go ahead an get your FICM voltage first? One thing I didn't like on the Livewire is it can't see that.

Any idea on your fuel pressure?

Did you just load the tune and go, or have you been running it a few days (not sure how much of a difference that would make, depending on how often the transmission has to shift)?

Anything different as far as payload, were you towing anything?
Last time the fluids and filters were done?
On Edit, sticking brakes or turbo issue?

These are the first few things that come to mind, I would rather not think its an injector going bad on you (depending on FICM voltage and Fuel Pressure).

[Dirty_Stroke]

Originally Posted by colo_dually

If you haven't checked, I would go ahead an get your FICM voltage first? One thing I didn't like on the Livewire is it can't see that.

Any idea on your fuel pressure? No I still haven't installed my fuel pressure gauge which is dumb I know. I do have an AD2 tho.

Did you just load the tune and go, or have you been running it a few days (not sure how much of a difference that would make, depending on how often the transmission has to shift)? I just loaded it right before I left

Anything different as far as payload, were you towing anything? Just luggage and a few fishing poles and a cooler. Probably no more than 3-400lbs
Last time the fluids and filters were done? Changed the oil last week, fuel filters on the AD have about 8k miles on em
On Edit, sticking brakes or turbo issue? If it's a turbo issue then I'll have a even better excuse to get a MAD turbo. I am going to check the brakes when I get back. Anyway to check turbo without pulling it off?

These are the first few things that come to mind, I would rather not think its an injector going bad on you (depending on FICM voltage and Fuel Pressure).

I sure hope it's not an injector. I know I should have already installed my fuel pressure gauge. It's brand new in the box sitting in my shop.

[colo_dually]

Payload wouldn't have made a difference in that case. When you can check the fuel pressure and FICM voltage.

What was your boost sitting at throughout the trip?

I think you would have noticed a turbo sticking, or a boost leak. Those are the two things I'd check for with the turbo.

If the brakes were sticking you may have noticed it taking a few more RPMs to get going with the loss of mileage you saw. But if you don't check it you can't rule it out.

The mileage increase some folks are seeing with the MAD turbos is the reason I'm making the switch this fall (if not earlier).

[Dirty_Stroke]

Thanks for the quick replies man. I won't be back to town and in my shop till next weekend, but I wanted several things to check. Could FICM voltage or clogged oil cooler contribute to the lost mpg??

[jbb421]

Did you fill it up at the usual place.... I know if i get bp fuel here my truck gets about 10 mpg vs 16 when i'm using shell fuel (the state trucks also use shell here)... I think its due to the fuel sitting in the bp tanks longer therefor building up water... just a thought

Edit: This isnt likely beings that you put fuel in it from two different gas stations.... mybad

[Northernl]

Look at the fuel you are using. In the winter we run #1 diesel. I get ~13.5mpg on #1. In the summer I get ~17.5mpg on #2 diesel.


Sent from my Autoguide iPhone app

[Dirty_Stroke]

Originally Posted by Northernl

Look at the fuel you are using. In the winter we run #1 diesel. I get ~13.5mpg on #1. In the summer I get ~17.5mpg on #2 diesel.


Sent from my Autoguide iPhone app

How do I know if it's number one or number two diesel? Also idk if I'm just paranoid now or what but I just drove it to dinner and it seems like its taking a very long time for the EGT's to cool down. I wasn't driving it hard at all on the way there and when I got there I let it idle for 2 mins and it still was right at 400 degrees. Could that be a sign of something? If the turbo was fixing to go out is there any early signs?

[jesilvas]

Was your AC on while sitting there at idle and what was ambient temp?