I've been hearing both sides of the story when it comes to "does having an aftermarket exhaust system boost your gas mileage." I've done a search on this topic empty handed so I figured I'd start a thread. Does an exhaust system increase, decrease, or keep gas mileage the same?

This question is due to my looking for a system with a nice, deep sound that doesn't getting overbearing after a two hour drive. Particularly a magnaflow system with dual pipes out. My main reason for getting an exhaust system is to boost my gas mileage by even 1 mpg. I do a lot of city driving so even a fraction of a mpg would help. I currently run the stock exhaust on a '08 4.6L FX2.

My two questions are as follow:
1) Will getting an exhaust system be beneficial at all?
2) What are your recommendations?

I don't want to get into any chips or reprogramming. That will be something for another day.

 

An exhaust *might* add .5mpg, if your lucky, I don't care what anyone says, they don't help 2-4mpg period. Most will get worse mileage because now you want to hear it. It will be louder, sound better, and perform a little better. I have heard the Roush Off-Road on a FX2 on youtube, and it sounded great IMO. I personally don't buy cat backs, I do custom work, its cheaper and gets it exactly how I want it.

 

I agree with the other post. You should see an increase but due to it being a performance exhaust you will want to hear it so you will have your foot in it more. If you can hold off from doing that then you should be Ok. I am very guilty of this. My gas mileage decreased since putting on my exhaust over 4 years ago.

 

I don't quite understand. My understanding from the replies so far is that magnaflow exhaust being a performance exhaust is quiet (quieter than stock?) but will potentially give me the small gains I'm hoping for. However, with the exhaust being quiet and my wanting a semi-loud exhaust, I will gun it cancelling out any gains I get. Hmm, I am more interested in the performance gains than I am the "loud factor" so I can handle the quieter setup. But I am a bit worried now, I checked the magnaflow website and the price I saw for a SI/DO kit made my stomach turn. Is there a cheaper alternative??

EDIT: I did a little more looking around and found the kits for ~$500 shipped. A little more reasonable but still a bit high for me.

 

just buy the muffler and take it to a custom shop have them do some custom bending nine out of ten times you can get it done cheaper this way. I have the roush off road exhaust and it is great loud when you want it to be and quiet when it needs to be (long road trips). But I have had the magnaflows which were good as well.

 

+1. Buy the muffler you want, and the tip(s) you LIKE and have a muffler shop do the bending. They can mig weld pre-cut pieces and 1/2 the price, you get the same sound, and if you didn't like the tips from the man. you get the look you want. If you're going for stainless steel, just buy a kit. It's a toss up. But if you just want aluminum, have it done locally.

 

For loud by a magnaflow 14" long with a 4" round body, for a good mellow tone get a 18", for a quieter, but still louder than stock sound get a 22" maggie. I just bought 2 14" and a x-pipe for $180, and after the new tips and pipe I *MAY* have $300 in the whole setup, catback is a WASTE OF MONEY!!(IMAO)

 

I won't bore you with too may of my past details but before I got my new truck (this past Saturday) I ran with the "rice club" in the compact market. I used to make intakes (actually manufactured them and powder coated them myself). I also had a website similar to driverFX and 4wheelparts.com.

The problem with modding a vehicle is that products like intakes and exhausts do get you better milage but it is minimal. There is no huge increase in mileage or power like most companies claim but it does change it and as mentioned above, we like it, so we play with it more! I had an 05 Jetta GLI prior to my truck I got this past weekend and I made an intake for it and modified the electrical system to the point I was getting 31MPG out of it.

Unfortunately it also resulted in a power increase which in turn resulted in lead foot syndrome. I was averaging 18-20MPG out of a possible 31. From the factory the car averaged 28MPG and that is what it was getting until I modified it.

 

I was looking at buying the Magnaflow cat-back for mine. Only because I get these things at cost. Does anyone here have the magnaflow? I am looking for the deep low rumble. I have the 4.6L Reg cab.

 

The vast majority of truck owners on here have magnaflows it seems. From reading up on these forums for the past few weeks I've only noticed a hand-full of flowmaster or other owners.

 

Mine should be here by thurs. I will run to the shop and fab it up, come back and post some vids.

 

Excellent! Thanks!