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Hey guys!
First time poster here! Glad to finally be on here!

Okay, I have a 2008 Chevy 1500 5.3.

When I bought this truck at 42k, I was getting 16.7 avg in town. I put the Rouch Country Leveling kit on it and some 275/65/20 Cooper Zeon LTZ's on it. Now my truck has gradually been getting worse fuel mileage and I know have 93k on it. Any ideas maybe why it's getting worse?

Do I need to do a tune up on it?

And where is the fuel filter located on these trucks?!

Thanks guys hope to hear from some of y'all!

-Steven
 

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2009 Chevy Z71; sounds fast.
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More friction to the ground and the computer doesn't accommodate for the larger circumference (two different thought processes, but both just as important as the other).

Original size tire is about 31.5"...the tire you are running now is 34"

Do this on your next gas mileage test. However many miles you travel on that tank, add 8% of the total mileage back to the mileage...for instance, if your mileage on the tankful says 320 miles, take 320 x .08 which equals 345.6, then divide that by the amount of gas you put back in. It should increase your number by a little bit. Be sure to use 8%.
 

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You may have taken care of these simple things, but thought I would mention them like cleaning the MAF and throttle body out, checking or replacing the plugs. Bigger/newer tires always usually mean more meat/weight and rolling resistance; and take into account the info Onlyina_Chevy mentioned.
 

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neo is on the right track. I suspect dirty TB from the oil ingestion and possible your intake valves are building deposits as well. I would try taking your TB off and use brake clean to clean the deposits off, then look into the intake manifold with a flashlight to see if it is coated in oil, if so get a good catchcan installed ASAP as this will help free up your piston rings so they are not sticking in the ringlands. Then of course the dirty air filter is the most obvious.
Any check engine light on? A failed MAF or upstream O2 sensors will cause you to run in open loop and run quite a bit richer.
 

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you dont really need to take the TB off, just take the air intake off and clean the throttle body really well by sticking your fingers with some cloth rags down in the TB. If it doesnt help then pull the TB and you probably would want to replace the gasket.
 

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Gaskets are all silicone O ring style and reusable, even on the runner side of the IM if you remove it.

Catchcan (loose term for them as so many are just empty containers) are installed inline with your PCV system and condense, coalesce, and trap the oil mist/vapors that cause detonation (the knock sensors pick this up and the PCM pulls ignition timing until it ceases, so that cost a good deal of power and fuel economy if your not able to run at optimum ignition advance).

Here is a good explanation on the PCV system and the issue associated with oil ingestion via the intake air charge:
http://www.revxtreme.com/index.php?rout ... news_id=20

Hope this helps.
 

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The throttle body is an easy removal/re-install I can usually clean mine in a few minutes and re-install it; though, you could keep it on and clean it as well. If you do clean your MAF make sure you use MAF cleaner as it is quite a sensitive piece also very fragile.
 

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With the increase in tire size, have you thought about a gear change? That would help, providing you could keep your foot out of it.

Ignore the DIC. On the next fuel up, calculate the mileage manually and see what you get.
 
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