Opinions on: After market Air Intake & Cat Back?


Asked by Jan 27, 2013 at 03:54 PM about the 2009 Chevrolet Avalanche LT2 4WD

Question type: Car Customization

I have a 2009 Chevy Avalanche that I purchases, used, in October 2012.  The truck runs great, looks good and has handled well in the limited snow we've had in the DC-Metro Area.  Plus, the truck keeps up w/traffic on 495 w/o a problem.  

Gas mileage is right where I expected it to be, in the 15/21 range.  However, I can't help but wonder if the claims of increased gas mileage for an air intake or cat back system would be worth the investment.  I plan to have the truck for the next 5 - 6 years (6 year loan); the Monstero was in my garage for 10 years.  So, hopefully, I'd be able to see a nice Return On Investment (ROI).

Looking through the various sites and videos, it looks like I could install the air intake in my garage.  However, I would need to drop the truck and parts off at my local mechanic's to have the cat back removed / installed.  

Have any of you, or those you know, added either after market option?  If so, did you / they see a nice ROI?  Getting 16/22 to 17/23 with the intake would be nice (extra 30 - 60 miles / tank, if I'm doing my math right).  According to the various parts sites, similar gains could be seen with the cat back (not sure if the mileage benefits stack, though).  An added bonus, if you will, from what I've read is that the truck gets a nice sound to it...beefier, if you will.

Many thanks, in advance, for your insight and input.  It's very much appreciated.

17 Answers


Yes! It really works. If you want the most out of your engine I would recommend both to be modified. The less an engine has to work to pull air in and push air out, the more efficient it will be and the more power will also be gained. It is a win-win. The only downside is if the truck is under dealer warranty, they may not cover any repairs because the aftermarket parts will void it. Good luck!

2 people found this helpful.

Thank you, Joef!


ROI no way , not before 6 yrs, unless your driving 40 50 k miles a yr on it,and thats a brand name, and without flow check of the system designed, by who a china factory ,they dont know you need some back pressure no doubt ,ROI will be to BP and aftermarket suppliers

1 people found this helpful.

Cat back did not help my gas mileage. It actually went down. But not due to the parts or installation. It was due to the beefy sound and my foot on the gas. Found myself taking off faster just to hear it sound off. Hopefully you will have more self control than I did.

4 people found this helpful.

You won't see any increase in MPG's. Hardly any increase in power and your warranty will remain untouched. If you want to increase MPG's try new plugs, new O2 sensor, air up the tires, drive slow and coast into stops.

2 people found this helpful.

exhaust does NOT increase gas mileage. does NOT. the intake will help in a lil power and maybe .5mpg better, but if you are looking for better gas mileage, check out a tuner like a Jet Performance tuner, those can increase your MPG's by 2-3mpg and your power too. but it costs a little more than the exahust, but is more beneficial than an intake...

2 people found this helpful.

i bought a tuner for my SS camaro, took me 189 days to benefit from it, so 1/2 a year about to ROI... i documented all my gas mileage though in an excel spread sheet at every fill up to see. something that may help you as well.

2 people found this helpful.

Thank you, everyone! Your input is very much appreciated!!


Tenspeed, You might not think performance exhaust systems could improve gas mileage, but they do. Stock systems, with narrow pipes and tight bends, often constrict the flow of gases coming out of the engine, backing up and choking the engine in its own exhaust. Cat-back exhaust systems use much wider and straighter piping to carry the exhaust out quickly with no impediments to the flow. As long as you're not hot-rodding around, these open- throated pipes clear exhaust from your engine more efficiently than stock exhaust systems, giving you more power and miles per gallon. They ABSOLUTELY increase efficiency. Dealers can also void a warranty if they suspect the mods you have added to your vehicle have lead to abuse or have lead to having detrimental effects on your vehicle. There is allot of grey area and some dealers are more mod-friendly than others but the warranty can be voided.

2 people found this helpful.

Your car / truck does relay on backpressure from exhaust to attain the gas mileage you are at... opening up the exhaust to a bigger pipe or aftermarket muffler for a better sound does typically 1 thing... take away from your torque. your HP will go up, but your Torque could suffer because of the decrease in back pressure, if you have an increase in HP and a decrease in Torque then your motor is working slightly harder to gain those numbers, thus your mpg's would go down. efficiency in overall hp and over all tq with other modifications then exhaust could be helpful for power, but not gas mileage. deleting cats has no impact on power or gas mileage. it is just clean for the ozone. if you don't trust me, go dyno your car / truck, take the cats off and put a straight pipe inplace of just the cats and re dyno it... you should see 0 gains, or MAYBE 1-2hp gain.. nothing significant to take them off.

1 people found this helpful.

as for a tuner, which is why i recommend it, it saves your factory settings and gives you on the plus side of up to 10% more power in HP and torque, so your motor is attaining those speeds easier and allowing your vehicle to attain better mileage, given that you keep your foot out of it... if something ever were to go wrong, you upload your stock tune and take it in for whatever warranty you have left (if any?) and they wouldn't even know. ON plus side, works as an OBD II code reader as well. tuner in my opinion and experience is a cheaper way to increase hp, tq and mileage.. go read some tutorials on some, Jet Performance tuner or diablo sport.

1 people found this helpful.

An efficient engine isn’t necessarily powerful. For example, the gas engine in a hybrid is incredibly efficient, but rarely are these engines considered “powerful.” Efficiency means that an engine gets as much energy as possible out of the fuel it uses. Therefore, improvements in efficiency improve power…but what if that power isn’t used to go faster? Having more power makes it easier to go faster.... But that power can also be used to make it go the same speed and use less fuel.


An intake system would be more beneficial to your overall gas mileage though. Small cars can benefit the most for performance exhaust. If you have a truck with a big V8, your engine is so powerful that it can push past a restrictive factory exhaust system pretty easily. However, if you have a small displacement 4-cylinder, adding a less- restrictive muffler can boost efficiency tremendously – sometimes as much as 10%

1 people found this helpful.

Most factory exhaust systems are way too restrictive and give much more back pressure than the engine actually needs.


joef - your answers sound like google to will exahaust improve gas mileage. I'm saying check your sources and experiences before you post material from other websites as a credible source, or at least site them.


All those claims are bogus. You will NOT see any increase in fuel efficiency. I have done these mods on multiple vehicles I have owned. None of them gained anything in terms of fuel efficiency.

1 people found this helpful.

Older cars yes. Intakes and cat backs on newer cars with ECU's DO NOT WORK. Aftermarket scams. The on board computer regulates air flow via air flow sensors in the intake and catalytic converters.

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