Hey all,
I have an 03 1/2 ton Silverado EX Cab Z71 with the 5.3. When I first bought the truck with 84K on it I was getting about 16 mpg on the high way.
Since then I have put on
Cat Back Flowmaster 50 series,
K/N Filter,
Airaid Mass Air intake tube,
Airaid Throttle body spacer.

After the add on's my mpg's have dropped with highway driving by about 1.5-2 mpg.

I have noticed a difference in the power, especially on low end torque and sounds awesome as well. With city driving I expected the the drop in mileage just because I was using that power and sound a little more. But I drive 400 miles once a week to work at 70 mph on the same road and yet the mileage stays the same.

I have thought about a tuner but the Diablo Sport tuner I had for my 99' with the 5.3 and same basic mods made very little power changes and dropped the mileage by 4-5 mpg. So I am hesitant to waste the money.

I have also been told to consider a new Mass air flow sensor.

Any ideas or suggestions?

 

well like many people have said that more power and better mpg normally dont go together. personally i have a K&N and cherry bomb muffler which essentially is a cat back because i cut teh old muffler off and its just the cats 2.5 ft. of pipe and muffler and thats it. but i noticed more mpg with the filter and low end torue. if i drove like a normal person i know my econ would increase but yeah. it has to do about driving and how much you treat each stop as an xmas tree and at green hit it. try using cruise control if your at a steady open road. it helps.

 

I agree Cam

"it has to do about driving and how much you treat each stop as an xmas tree and at green hit it"

With the performance mods in place your are more likely to be heavier on the gas because you are accelerating to the tone of the exhaust...

 

yeah. thats why guys insurance is more in the first 8 years we drive. hehe... o well. i just try n stay calm and believe me... you can get fair mileage off a tank just use cruise control.

 

Can you tell me if it is possible to turn off the cylnder drop on a chey 6.0?

 

folks, there is a thing called O2 sensor. O2 sensor senses more oxygen in the exhaust. Rats to ECM about this. ECM is dumm and thinks that engine runs lean and lets more gasolino into the engine to enrich the mixture. This results in more power.
More O2=more Gasoline= More power. no matter what you do or say, you can not beat the ECM. You want more power - it is a gasoline powered engine, it will take more gas to give more power.
Same goes for MAS/MAF sensors. This is how the gas engine works. Now, on dumm carb engines, where there is much more room for improvement, he-he......

 

First, Ukrkoz is a voice of experience, and what he's saying makes sense to me.

Second, my Diablosport Predator hasn't shown me a significant improvement in gas mileage.

 

I have many times heard the equasion (more flow = power witch = more fuel)
+ more power means HAMMERDOWN WOOOOHOOOOO!

 

have you tried disconnecting your battery cables since you put the mods on the truck. if not try that and let the computer reset so that it will adjust to the new parts in the next 75 miles or so and see what happens

 

Thanks hondaracer27 for the idea I will give it a shot. Can't hurt anything.