[MacBradley]

So I am not very knowledgable about cars, and I just bought an 08 v6 Mustang since my old car got totalled...

Anyway, what I was wondering is how an aftermarket muffler would affect mpg on my car. Upon calling a couple local places most said that on newer cars less restrictive mufflers lose gas mileage (something about new cars having low compresison, don't know what that means). I was wondering if some of you guys could help me out here, because I'd like to get better gas mileage, and wouldn't mind a better sound and a couple horsepower, but I don't want to lose gas mileage, I already drive tame enough to get 19 around town with no traction control.

[Cox]

get a AM Muffler. The local places do not know what they are talking about :P

[drjeff]

I put a GT take off muffler on my V6. I like the sound and I think I feel a little difference in giddy-up. I definitely have not noticed an increase in gas mileage, perhaps even a small decrease, but I also switched out the muffler in December, so it's been running on winter gas. I won't know for sure until spring. It would also help if I didn't drive like a lead foot most of the time.

[jmmckay]

I swapped my stock V6 muff with a Flowmaster American Thunder, no noticable diff. in gas milage buts sounds GREAT! The swap took 30 mins in my driveway..

[FYouGitive]

The FRPP M-5230-GTA muffler I replaced the standard one with sounds so good to me, I'm afraid I get a little less MPG. I'll never know for certain, 'cause I can't go a whole tank without CRANKING IT ON at least a few times.

YouTube - V6 Mustang dyno pulls 12 January 2008

YouTube - 2006 Mustang V6 Exhaust sound