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-   -   Installed a magnaflow now loss of mpg (

BadHazard 07-28-2012 01:38 PM

Installed a magnaflow now loss of mpg
I had a 3" straight pipe on, had to put a muffler on, bought a magnaflow straight through. I was getting a hand calculated 15 mpg before the muffler, now I barely brake 13. Its been on for about a year. Before the install my lie-o-meter was at 17 to 18, even that has dropped. Nothing else has changed.

Can a bad egr valve be a problem? Or isnt there another thing similar to that, that can cause mpg drop?

RcsbHemi 07-28-2012 03:18 PM

Have your driving habits changed after installing the muffler? I ask because my MPG went down also but I blame myself because I always want to hear my exhaust, especially under acceleration.

HEMI450HP 07-28-2012 09:57 PM

Running without a muffler is going to give more power and better mileage, so I would expect to lose mileage reguardless of which muffler you added.

BlackHemI 07-31-2012 02:09 PM

weird...i had no muffler and went down to 11.5-12.5 mpg. with my maggy it is 12.5-14 and this is hand calculated...i find it hard to believe you get 15 with your 4x4!!

crusher 07-31-2012 03:54 PM

i would say you have a foot problem thats related to your hears, we all had that problem with the mufflex,.. but if your sure thats not the probleme, did you change your plugs, clean air filter and or replace it and perform a tune to your truck lattely??

S.C. Express 08-02-2012 02:02 AM

Checked tire pressure lately, and did you factor in the weather lately? I don't know about Montana's climate, but it's hot and humid as hell out here. There is an easy 1-2mpg difference from driving in hot weather vs. cooler weather. I paid close attention to my mpg's on a long trip I took recently. Mid 80F degree weather gave me much better mpg's than 90+F weather.

70x7 09-23-2012 07:15 PM

Same thing happened with my muffler swap.
I attributed the first couple fillups to the foot pedal cause of the sound, but the mpg calculation has consistently shown about 1- 1.5mpg drop and its not cause of the sound anymore since I have purposely let off on the throttle more.
Was getting about 15.5 before and now it hits 14 or just a tad over...

moparornocar72 09-23-2012 09:54 PM

I would run some cleaner through the top end such as seafoam or bg branded intake cleaner. But as mentioned anytime u go from no muffler to muffler ur going to lose mpg

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