I can tell you the fuel mileage is what it is on a 6.2. I have every thing done with my truck but gears and boost.

I hooked up HP tuner and only removed the AFM in the tune and touched nothing else. My fuel milage didn't drop one bit.

Then I tuned it with nothing else. Just changing the PE and not locking the converter in gears 1-4 is worth it's price. The Delays in PE are crazy and make your truck feel so lazy.
But after the tune I might have picked up 1 to 2 mpg. I could get 20 pmg with bigger tires.

Then I added E85 sensor, I lost 3-4 mpg depending on my foot. BUT the power it picked up was clearly there and worth it.

Then I hurt a lifter so I did a 218/226 cam and had a local machine shop port the heads. I lost solid 2 mpg.

Next came headers and a wideband. No change in mpg.

Lastly Airad Jr intake and modifidy the stock air box to open it up. I got more air into the engine but gas milage didn't change.

Do all the mods because it will make your truck run better but your not going pick up a ton of mpg. Lower it and put lighter tires and wheels if you want mpg.

I have a ZR1 95mm throttle body and LT2 intake to put on the engine after I get it back from the machine shop from a bad rod bearing. But I don't think I'll pick up and mpg's from that.

 

I noticed considerable gains opening up the catback, whether it be through swapping the stock muffler for a free flowing muffler and cutting out the flapper valve (got 2 mpg when I did this) or changing to an aftermarket cat back. Either way adds considerable mileage on these trucks.

 

I’ll be the counter point and say nothing I ever did to my 14 did anything to increase mileage. The cat back, removing the flapper, headers, tune. Nothing.

 

Who you gonna trust? The guy with no profile pic or the guy with booby pic?

Has anyone tried to see how much increase in MPG they would get with a drop? I would assume that the smaller/lighter tires and the less underneath resistance you have may net you a mile or two?

 

One is trying to bribe you and one is trying to remain agnostic.

 

***** win every time.

 

I've got a 2013. I get 10-12 around town and 15 on the interstate with 93 in Florida. That 8 speed and direct injection sound like they're helping quite a bit.

Is the exhaust different though? I can't imagine that 3.5" factory cat back is that restrictive.... Mine is loud, almost too loud for my taste and that's with the resonator.

 

The factory exhaust on mine was still 3.5"

BUT

The factory exhaust has the butterfly valve and it is very restrictive. There are picture of it, I just don't have time to dig it up.

 

Definitely does

Surprising you didn't. I did and Sam at AMP said he has had customers with trucks call him after doing a cat back and say they also noticed an increase

I got a 1-1.5 mpg bump changing the stock 6.2 muffler (with no flapper) to a magnaflow verified by my mileage per tank going up around 30 miles per tank

When I had the stock 5.3 exhaust and flapper still in and went to a magnaflow and no flapper I saw closer to 2 mpg.

However, my neighbor didn't see any gain he said, be he also only drives about 5 miles on most trips and his other trips he said he drives foot to the floor for a couple of hours trying to do 100 mph the whole way if possible... so.. he isn't going to see the change. So I dunno man. Could be other factors in why you didn't see a gain. Not sure. You also had some tuning struggles that may have been part of it all.

LOL

I didn't notice anything with my drop. I thought the same thing but I don't notice anything there.

Que?



The flapper valve is the main issue. The stock muffler doesn't flow that well (not the worst thing in the world but not great) but the flapper is the bigger problem. It takes up a really considerable amount of the pipe opening, approx 80 percent in my opinion, and IF it does blow all the way open under heavy throttle, it still restricts probably close to 50 percent. I'll post a video of it below.

When I had the flapper, I locked it full open and noticed no difference. But when I had the stock muffler cut out and the flapper and a magnaflow put in, I noticed a big difference, and that's comparing to a locked open flapper.

As for fuel mileage. The engine design, the higher compression ratio, the DI, the aero of the truck body and a few other factors really help these newer trucks. Mine is a 2014 with a 6 speed. It gets about 6 more mpg than my 2004 5.3. The 8 speed may help a touch over the 6 speed.

What's most impressive to me is the 6.2, it gets even better MPG than the 5.3 it seems


I got it. I love posting this video lol

 

Wait,....wtf is this voodoo. I've never seen or heard of this....ever. It just rained so not going there now, but Imma look under the truck and see what I got. That seems so got dang extra on GM's part...wtf.