Magnaflow dropped mpg

[Antjhony]

has anyone noticed a drop in mileage after they put an aftermarket muffler on? My instant readout mpg has dropped 3-4 miles per gallon after the muffler install. And I've put around 1000 miles on it since. I also have a k&n drop in

 

[JoshTRD]

has anyone noticed a drop in mileage after they put an aftermarket muffler on? My instant readout mpg has dropped 3-4 miles per gallon after the muffler install. And I've put around 1000 miles on it since. I also have a k&n drop in

im in the same boat mate! i have the Borla bolt in muffler... and after installing i felt a lose in torque so i also installed a k&n drop in to allow more air flow.....but yea i my average mpg sits at a firm 24 and the highest being 25....

 

[JoshTRD]

has anyone noticed a drop in mileage after they put an aftermarket muffler on? My instant readout mpg has dropped 3-4 miles per gallon after the muffler install. And I've put around 1000 miles on it since. I also have a k&n drop in

but i don't let the computer determine my mpg...when i drive i keep my Revs in the ECO range so it doesn't really bother me that the computer says average mpg is 24.....sometimes i wanna drive hard and sometimes i wanna drive to save gas....so its not even accurate.

 

[Antjhony]

But my computer average dropped 3-4 miles after my muffler install.. I wonder why my mpg went down after installing a high flow exhaust that doesn't make sense?? Does anyone know where I can buy a used factory muffler

 

[Matthew]

You're probably pressing the gas pedal harder since it makes more noise now without realizing it. A simple muffler replacement won't touch MPG.

 

[Antjhony]

No I'm talking about setting the cruise on highway the car gets worse gas mileage now on same highway with aftermarket muffler

 

[trdriky91]

I have a S+ 6speed with K&N intake with a TRD axle bolt on exhaust and I'm averaging 29.76 mpg my computer says 29.2 mpg so it's close. When I'm actually pressing on the gas pedal to the floor I'll get at least 27.6mpg. My mpg didn’t really make a difference from all stock to what I got now. I kept all my stock muffler n intake so I can reuse it for the winter.

 

[Antjhony]

Does anyone have a stock muffler they want to sell?

 

[perrijman89]

I'm still getting around 30MPG here. Borla Axle Back, K/N Cold Air Intake. I also had the resonator cut off and welded in a piece of pipe. No issues here! Like I said still around 30-31MPG.

 

[Nguyen925]

but i don't let the computer determine my mpg...when i drive i keep my Revs in the ECO range so it doesn't really bother me that the computer says average mpg is 24.....sometimes i wanna drive hard and sometimes i wanna drive to save gas....so its not even accurate.

You're dash MPG average really says 24MPG? Do you happen to reset it every time you fuel up? I imagine the worst contributing variable in low MPG is the initial accelerating from a stand still. My on board computer tells me I average 34-38 MPG and I keep my RPMS under 2,000 when I'm accelerating. That's also 40% city/60% Hwy. Also don't just use the on board MPG as a very accurate tool, many times I've calculated my MPG (I keep a fuel log in order to see if there's something wrong with my car) and the MPG shown on the dash is very generous average. You are most likely averaging 2-3 MPG less than what the dash is telling you, FYI.