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My gas mileage

 
Old 03-04-2019, 04:49 PM
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Default My gas mileage

I installed a Flowmaster Delta 40 and a cold intake on my 2003 5.4L. I don't drive much so 1 had 159 miles traveled since my last fill up the muffler and intake went on a 76 miles. My gas mileage worked out to 10 MPG. I didn't get a figure prior to the changes I have been getting on it liking the sound and response. I have 4.10 gears is 10 MPG normal? 126,700 miles on the truck.

I have a 36 gals tank and the gauge showed 1/4 I fill it up it took 16 gals. The gas gauge normally this screwed up?
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Old 03-04-2019, 06:14 PM
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That muffler is chambered, so your going to take a hit in mileage. Chambered is the worst you can do AFA mileage and performance. They make it that way for a unique sound, they sound good if your into that sort of thing... you'll pay for it lol. You'll get better mpgs and performance with a straight through design like the factory muffler. That manufacturer has some straight through designs, the DBX Laminar flow is one. Most mufflers are straight through designs. The one you picked isn't.
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Old 03-04-2019, 07:05 PM
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It seems to be a lost art on how to figure out fuel mileage. You CAN NOT base it off of the gauge.... EVER. They are not accurate, at all.

Here's how to do it the most accurate way possible. Go to the gas station, an fill it up all the way. Then reset your trip odometer. On your next fill up, pay attention to how many gallons you put in the tank. See pic below.... in this case, I put 21.009 gallons in.



Now climb in and look at your trip odometer..... in this particular case, we have 308.7 Miles.....




Now take 308.7 miles, and divide that by 21.009 gallons, and you've got your accurate MPG's.




So... 308.7 / 21.009 = 14.69 MPG

Last edited by white89gt; 03-04-2019 at 07:09 PM. Reason: Fixed Pic
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Old 03-04-2019, 08:25 PM
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White, he did it correctly. Said drove 159 miles, filled with 16 gallons. That is 9.94 MPG.

Without knowing what you mileage was before, hard to say what the problem is.
And these 5.4 get really thirsty really fast when you "get on it". 4.10 don't help either.

You need to track your mileage for several tanks to get an accurate reading.
See my sig for my mpg over 28,000 miles.
I have gotten as low as 9.8 mpg and as high as 22.4 mpg.

As for the fuel gauge, hard to say. could be a bad sender.
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Old 03-04-2019, 09:21 PM
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And don't forget about adjusting for the difference in tire size from stock or gear ratio too. If that stuff isn't corrected in the PCM.
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Old 03-04-2019, 10:05 PM
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Did you not like the free cold air intake that originally came in your truck? I'm guessing you installed a K&N? Ever notice how it's open under the hood so you're sucking in hot air from around the engine? Yeah that oem intake; did you notice where it was Plumbed to? Went thru the inner fender. It's sucking in fresh air outside the engine bay. But yeah I'm sure the air from under the hood is colder lol
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Old 03-05-2019, 08:42 AM
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These trucks do come with a decent air intake system, why people screw around with that is beyond me.
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Old 03-05-2019, 09:32 AM
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Yep... Gotts mod, keep a clean filter in it, and done.
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Old 03-05-2019, 03:26 PM
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Attempts to get more air through the intake, but plugs up the exhaust with a chambered muffler.....that doesn't compute lol.
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Old 03-05-2019, 05:17 PM
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Originally Posted by JCR 56 View Post
These trucks do come with a decent air intake system, why people screw around with that is beyond me.
So people like me have something to post about.
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