Will this give my SUV better mileage?

Nope, will increase noise, may increase power at wide-open throttle. As someone else noted, the added noise probably makes people go easier on the gas, increasing milage. But you can do that without spending $800.

No it will not. Almost all vehicles come from the the factory with fuel economy in mind, after all there are CAFE standards to meet. You likely will not get any fuel mileage increase.

You should make these modifications if you relish the "boy-racer" sound level that is likely to result.

You shouldn't do these mods if you think that it will increase your gas mileage--because it won't.

It all depends on what your real priorities are.

Hey, "boy-racer" sounds fun! Really though... I'm married with children, have need for a full size suv and am really interested in improved mileage. The logic I was given seemed to make sense - easier to get the air in, easier to get the exhaust out, slightly improved power - all giving slightly better mileage. There was also a conversation about putting the computer back in "learning mode" so it would relearn how the engine breathes with the changes. Believe it or not, the parts I've researched will not be much louder than stock. I'm NOT looking for a hotrod! I just have no experience with this and can't seem to find any real data anywhere.

It won't make the air easier to get in and out. The air flow is already very good. Your mileage will remain the same, except that you will have wasted $800+.

"... I'm married with children"

Al Bundy's married with children; what would he do?!

But Seriously, the mechanic needs a Corvette payment, and you're it.

He'd push his trusty Dodge all the way home after it broke down. :D

The logic I was given seemed to make sense - easier to get the air in, easier to get the exhaust out, slightly improved power - all giving slightly better mileage.

In both cases the key word is "slightly." It is far too slight to pay for itself over the life of the car. It is likely too slight to measure the mileage and you likely would need some very sensitive tools to measure any power increase.

Back in the grandpa's days, most cars had restrictive air intakes and exhaust. The manufacturers have corrected that a long time ago, but grandpa's advice still lives on long after grandpa.

What's with needing a "new cold air intake"? I've been driving since I was 12 (42 years) and never heard those words. Restrictive as in crushed? plugged? or some notion about better mpg? If it's the former, get it changed out and do the tailpipe and hangars while in-there. I have had the work I'm suggesting done many times on Subarus and never for more than $250. That's a change-out in under one hour at minimal shop time (labor) of $70. The dollars your talking are way way off. If you don't need 'worn out' replacement, put your bucks in a car-only fund and use it when you really need it. Google some research on what really ups mpg. It's not mufflers. For a mechanic to apply the words "very restrictive" to a stock muffler, tells me your being hustled for a sale.

You can buy an aweful lot of gas for $800. My bet is that even if it gave you 2mpg increase, you would never recover the $800

I agree that you may never recover that $800. It's easy for you to compute that since you know how many miles/year you drive, your current vehicle mpg, and the average price of gas.

I have doubts your mpg will increase. However, if it does, you might want to take the 5 minutes to see how many years you'll need to keep the car just to break even on that $800.

At $3.00 per gallon... about 18 months. Granted, gas isn't quite $3.00/gal right now. 2 years at the outside to recover my investment "if" it works. 2 miles to the gallon may not sound like much. Believe me... in a big suv, it makes all the difference in the world. The question is, "Would these changes actually make the improvement to the gas mileage?" If yes, I will easily recoupe the $800 dollars. I suspect the truck will be more a little more fun to drive too.

And that's exactly why it won't work. If some minor intake and exhaust fixes would increase a SUV's milage by 2 mpgs, that would be HUGE, and all the car makers would be doing it already. You've proved our point.

I just don't agree with this statement. I know I'm going to catch flack from you guys for this. There's always a better way to build a mouse trap. You just have to know what you're designing it to do. This doesn't mean that these changes will work. I was just hoping that someone with some technical knowlege might be able to give me some kind of a cold hard facts response to the question or have any real life experience with this sort of thing? In searching the web, I find repeated horsepower and torque increase data. I find many suggestions that mileage will increase, but no real data (or someone saying, "I did it and here was my result.") to support the mileage part of it.

If you are so convinced of this, why did you post the question. Not one of the responses here has said you will get better mileage, but it sounds like you are going to do it anyway.
So, you are saying that few guys have figured out a way to increase mileage that the hundreds of automotive engineers with their research budgets in the millions couldn't come up with. I'd go all the way and add the pulstar plugs and fuel line magnets too.

Don't forget the voranado intake too .

"...some kind of intelligent response..." Hmmm, I thought that's what you were getting. We've noted the potential for additional hp. If mpg increases were real, you find lots more than 'suggestions' that it would happen. You'd find cold, hard facts. None there? There is a reason.

My appologies! You are correct.

My Mustang is pretty heavily modfied; supercharger, CAI, long tube headers, Off-road X-pipe, single chamber mufflers, 75mm Throttle Body, bigger plenum, and a custom ECU tune. 4.10 gears (31 spline), GT500-spec Trac-lok LSD, chromemolly axles, Centerforce clutch, Brembo 4 pot brakes up front, 2 pot brakes in the back, Eibach Sportline springs, and Koni adjustable struts/shocks (yellows).

My Bronco has some work done to it as well. GT-40P heads, K&N CAI, shorty headers, straight pipes, Dick Cepek 4 inch lift, 33 inch Goodyear MT/R's, and 4.56 gears

I'm pretty familar with most aftermarket accessories.

Thanks, I edited my question above. It came out the wrong way.