MPG is starting to REALLY suck!!

[Bumpin' Yota]

Well I've been noticing that our truck has been getting worse and worse mpg. When bone stock and new, she'd get about 14-15 towing a 3000lb trailer. By 35,000 miles it was down to 13.1-13.8.

ZooDad Mod at 38,000 miles brought it back up to 14.2-14.7

Put on my 4" turbo back (I havent put on the down pipe yet, just the cat delete, 4" cat back, and the high flow muff oriented for quietness) and am at 41,000 miles. (Anyone wanna lend me a tranny jack or a sawzall?)

So I go for a nice little 300 mile drive today expecting 14-15 and wham 12.1 mpg! ARRRG! Totally granny footing it too. The tires are actually a little over inflated, including the trailer's, but still within safety margins. Bearings are good in the trailer. Top speed seen was 69mph the whole trip.

Origional Fuel Filters
Today was HOT with temps around 95* w/90% humidity all day and the 300 mile drive was done with the AC blasting.


Those are the things I can think of that might have negatively impacted my fuel mileage. Where should I start?

[Dave]

definately change fuel and air filter. Also clean the EGR that will help alot

[DoubleDpsd]

41k on original fuel filters?! check your filter minder and see if it has moved. Maybe drain the fuel/water seperator?? My bet is defineitly those fuel filters though cuz Im getting 15mpg at 70mph with 35's.

[Ditty]

You definately need to change the filters. I changed mine and I'm up from 15-16mpg to 18-19 mpg.

[Big AL]

I agree with fuel filters. Air filter needs to be checked also.

[Bumpin' Yota]

the filter minder on the air filter says completely ok


Fuel and air filters will be done today - how do i refill the bowls after I change the fuel filters? The 6.0 bible give great education on where things are but not a dang thing about how to actually do anything to the engine.

How do I keep air from the injectors and refill the bowls on both the secondary and horizontal fuel filters?

[Ditty]

In my 7.3L, I just pulled the old filter out with the bowl full, and popped the new one in...no draining or anything. That's my 0.02 though.

[Logan]

You may have done damage to the injectors while not changing the fuel filters. That can drop your mileage real fast. I had one go down 5% and noticed it pretty quick in the fuel mileage department.

Just do the one on the frame rail first. Cycle it a couple of times and even crank it. Then do the one on the top. Should fire right up.

[06TWO50Diesel]

Fuel Filters ftw... I changed mine and noticed a difference as well. Going to get full service on my rig, brakes and all, soon. I'm seeing 14-15 regularly in my diesel with 35" tires. (06 with a few mods as well- as you can see in the sig) So you should just right back up with the numbers after your 6.0L is breathing a bit better all around.



-nate

[quick26]

i took a trip yesterday and on the way there i was averaging 10.5mpg but some hills and stop and go were to blame, but on the way home when we got to nothing but open road i reset it and i was only up to 12. the trailer weighed in at close to 7000lbs. my buddys 7.3 was pulling close to the same load and he was averaging 18mpg. i just cleaned the air filter, and have maybe 5k on the fuel filters