Out1aw

iTrader: (1)

Is it true or just a myth that replacing your stock muffler with something like a Flowmaster will actually improve gas mileage?

camaroextra

iTrader: (10)

not crapmasters, but any exhaust that provides LESS back pressure than stock will improve gas mileage.

Out1aw

iTrader: (1)

such as...

camaroextra

iTrader: (10)

SLP loudmouth for sure. any muffler that has a strait through design, instead of the "rat maze" for the exhaust gasses

2K2WS6TA

iTrader: (2)

FWIW I lost 3 mpg for a week after headers, it's back to 19 mpg now (seems no matter what I do it stays at 19mpg)

camaroextra

iTrader: (10)

well you probably drove faster for that week.

2K2WS6TA

iTrader: (2)

you're probably right

Out1aw

iTrader: (1)

The only problem is it's going on my truck, so the drone of a dumped bullet or 1 chamber would be crazy!

kyles2000z

iTrader: (8)

everyone knows that you always loose gas mileage after the install of an aftermarket exhaust. this is simmply bc driving style changes...you wanna hear that V8 roar, so ya give it more gas more often, resulting in crappy gas mileage

LS144

iTrader: (7)

You will definately lost MPG, simply because youll always wanna be at WOT due to the sound. IT happened to me and all i have is a cutout on stock pipes and manifolds. Its going to be terrible when I get my LT's and true duals.

Ric

in the event that you CAN drive then as you do now, you'll notice an increase in mpg. As stated though, we all love to hear our engines, so....

Scotty-Z

iTrader: (5)

If you can drive normally, you may see just a bit of mileage increase. Nothing huge at all, but you will maybe see a bit.

Now if you changed to something like longtube headers with a new mid-pipe (y-pipe for us F-body guys) and new exhaust, then you'd see a bit more. But as has been mentioned, we all love to hear that exhaust, so gas mileage ends up going down.

WILWAXU

iTrader: (6)

That has more to with the out of wack tune than the difference in flow.

Drew's TA

After mac headers and SLP Loudmouth I actually noticed an increase in MPG by about 3 or 4 MPG on the highway. I have seen 31 MPG on a 4 hour trip.

Now in the city when I am on it all the time I get very bad MPG, close to 10-15MPG, but if I keep my foot out of the throttle I see about 18-22MPG. Just my observations.

99Hawk262

iTrader: (19)

I picked up 3 MPG after the LT's and TD's went in. Yes I love to hear it, but I still noticed the increase. I drove mostly highway at that time.

98camaroLS1M6

iTrader: (35)

Yeah, a better flowing exhaust will richen A/F and so you may use a little more gas until you tune it.

GuitsBoy

iTrader: (4)

Ive lost maybe 5 mpg highway with mods in sig. A good flowing intake and exhaust as well as a good tune will do wonders for keeping your milage up.

silverTA2002

iTrader: (1)

Agreed with the above.

Also, there are other mufflers out there that are straight through, but not ridiculously loud (like loudmouth).

Dynomax ultraflow is one. Probably the "quietest" straight through muffler out there. Still much louder than stock though.

ls1z28chris2

****, 93 octane is 2.99 around here. No WOT runs for me... At least not until I get a beater.

GuitsBoy

iTrader: (4)

Its 3.30 here today. Just jumped 30 cents this morning. And I daily drive 80 miles round trip