Where has my milage gone?

D

dirtymax66

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Joined
Jul 26, 2009
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21
I keep up on my maintenance with oil and fuel filter changes every 5k. I change my airdog filters around every 10k. I have intake exhaust efi street tune airdog 2 and pcv reroute egr blocked. Truck has 161k on it and mileage has never been never been so bad. I jus drove from okc to tulsa today and its about 120 miles roughly and i needed to fill back up before i got there. Im confused why its getting such bad mileage. I recently cleaned the air filter and fluid changed jus a weeks ago. Any opinions?
 
Winter fuel possibly.

Didn't see where you said what mpg's you were getting.
 
Sorry was getting around 16-18 highway and it dropped to bout 9.5-10 on a good day. Plus i drive really slow and easy since its my dd. Someone suggested i do a compression test to check for a weak headgasket. Sound plausible?
 
It seems a little weaker but i think that's because i went to a more street friendly tune
 
look for a boost leak. Check the lower part of the left side tube for a hole rubbed through it
.
 
I'm surprised no one has mentioned injectors. Though they're usually a gradual fall in fuel mileage.

Have you checked the balance rates?
 
Has it been getting bad MPG since you put the IC pipe. Maybe like someone said before a boost leak from when you installed the new pipe. I would check that out and check the balance rate. Also change fuel filter. You might of got bad fuel some place.
 
being that the truck is an 05 i doubt it is the injectors. You said you went to a more street friendly tune. Did Mike write that tune or where did you get it? A boost leak that could cause an a drop in mileage like you have would be noticable without a doubt. If the mileage started declining around the same time you put the new tune in, i would bank on that being your issue
 
Just an FYI... LLY's are not immune to injector issues. They are by far the superior design, but they are not immune to issues.
 
Clean your MAF sensor. Very common for it to get dirty and creates MPG issues, esp. if you have an oiled filter.
 
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