Magnaflow And Mpg's

farmallcub · March 18, 2009

I put a 2.5" in and out, 18" long Magnaflow on the truck the other day.

I've got an 09 with the 4.3L that has been getting around 18mpg.

I took a trip (165 miles) yesterday with the new muffler and checked my mileage. I was surprised to find that I got 20.5 mpg. Could the muffler have done that much?

The truck felt better, I used cruise control on the PA Turnpike and the four lanes (not a change of habit), I tried to drive like I normally do.

I had installed a K&N filter when I bought the truck with no noticeable difference, which is what I expected. I just like the free flowing filters over the paper ones.

I can't wait till Blackbear can tune my PCM! Hint, Hint......

Once that is done, I think this lil six will do just fine.

66nova · March 18, 2009

I put a 2.5" in and out, 18" long Magnaflow on the truck the other day.
I've got an 09 with the 4.3L that has been getting around 18mpg.

I took a trip (165 miles) yesterday with the new muffler and checked my mileage. I was surprised to find that I got 20.5 mpg. Could the muffler have done that much?

The truck felt better, I used cruise control on the PA Turnpike and the four lanes (not a change of habit), I tried to drive like I normally do.

I had installed a K&N filter when I bought the truck with no noticeable difference, which is what I expected. I just like the free flowing filters over the paper ones.

I can't wait till Blackbear can tune my PCM! Hint, Hint......

Once that is done, I think this lil six will do just fine.

No

BuckFeverZ · March 18, 2009

At best, a cat-back system might net you .5 MPG.

farmallcub · March 18, 2009

Hmmmmmm........

hmb2016 · March 18, 2009

might be due to the summer gas mix?

66nova · March 18, 2009

At best, a cat-back system might net you .5 MPG.

+1

Especially on a GMT900 truck. The exhaust on these trucks are not that bad. Are they the best flowing systems available, no. But they meet or excede the needs of these trucks. Some older trucks you can't really say this, especially the GMT400 or older.

Think about it for a second. With GM's current state and the state of the market when fuel economy commercials rule, do you really think GM would not put a magnaflow (or other exhaust) on there truck if they could even manage to get another 0.5mpg out of it.

Most likely senario, is...the type of gas, wind, driving style, motor is breakiing in...........so on.

GARB55 · March 19, 2009

At best, a cat-back system might net you .5 MPG.

+1

Especially on a GMT900 truck. The exhaust on these trucks are not that bad. Are they the best flowing systems available, no. But they meet or excede the needs of these trucks. Some older trucks you can't really say this, especially the GMT400 or older.

Think about it for a second. With GM's current state and the state of the market when fuel economy commercials rule, do you really think GM would not put a magnaflow (or other exhaust) on there truck if they could even manage to get another 0.5mpg out of it.

Most likely senario, is...the type of gas, wind, driving style, motor is breakiing in...........so on.

+1

2k7gmcsierra · March 20, 2009

Wish it were that easy but not likely.......

farmallcub · March 20, 2009

I wonder if it might also have something to do with my staying local long enough to get a few fill ups at a station that doesn't advertise 10% ethanol in their fuel. I've been on the road and stopping at Pilots and Sheetz and they both use ethanol.

MikeInCtown · March 20, 2009

First off, you do get better mpg with free flowing exhaust. I doubt it was 2mpg though. probably a combination fo some dry warmer air combines with some favorable winds.

Now as to the complete misconception that GM would put it on the truck if it helped. GM is in the business of trying to make money. They do that by offering a standard product that will appeal to the most possible people in order to generate sales all the while lasting a long time in order to generate the fewest warranty claims. In order to help this along they sometimes put cheaper products on the vehicle than they could put on it otherwise. If it was ONLY about MPG and nothing else, every single truck would have a CAI, some type of performance tune, a free flowing dual exhaust, tonneau cover, e-fans since they were invented, underdrive pulleys, MSD wires, ACCEL SuperCoils, 3.23 gears and every other product designed for mileage and power. To somehow think that GM would have done it if it worked, so if it's not on there it means it doesn't work is absurd.

97SierraGMC · March 20, 2009

First off, you do get better mpg with free flowing exhaust. I doubt it was 2mpg though. probably a combination fo some dry warmer air combines with some favorable winds.

Now as to the complete misconception that GM would put it on the truck if it helped. GM is in the business of trying to make money. They do that by offering a standard product that will appeal to the most possible people in order to generate sales all the while lasting a long time in order to generate the fewest warranty claims. In order to help this along they sometimes put cheaper products on the vehicle than they could put on it otherwise. If it was ONLY about MPG and nothing else, every single truck would have a CAI, some type of performance tune, a free flowing dual exhaust, tonneau cover, e-fans since they were invented, underdrive pulleys, MSD wires, ACCEL SuperCoils, 3.23 gears and every other product designed for mileage and power. To somehow think that GM would have done it if it worked, so if it's not on there it means it doesn't work is absurd.

66nova · March 20, 2009

First off, you do get better mpg with free flowing exhaust. I doubt it was 2mpg though. probably a combination fo some dry warmer air combines with some favorable winds.

Now as to the complete misconception that GM would put it on the truck if it helped. GM is in the business of trying to make money. They do that by offering a standard product that will appeal to the most possible people in order to generate sales all the while lasting a long time in order to generate the fewest warranty claims. In order to help this along they sometimes put cheaper products on the vehicle than they could put on it otherwise. If it was ONLY about MPG and nothing else, every single truck would have a CAI, some type of performance tune, a free flowing dual exhaust, tonneau cover, e-fans since they were invented, underdrive pulleys, MSD wires, ACCEL SuperCoils, 3.23 gears and every other product designed for mileage and power. To somehow think that GM would have done it if it worked, so if it's not on there it means it doesn't work is absurd.

And my friend you thinking that every thing you just listed there will net you another 1.5mpg consistantly is absurd. In years past, I would have somewhat agreed with you, but we are living in a different time now. I fully understand that it's not ALL about mileage, it is a balancing act between mileage, power, reliability and cost (for GM and the Customer).

And GM has done most of the things you listed and heavily marketed a vehicle with those upgrades. It's called the XFE. I'm not sure about everything they have added, but I know a few...3.08 gears, a six speed transmission, lower ride height, tonneau cover, CAI, low rolling resistance tires, and it seems like a few other things. They did all of this just for an advertised 1mpg gain. So you are telling me that all they had to do is put a magnaflow on it?

Free flowing exhaust will net you gains if the stock exhaust is overly restrictive. On the GMT900 trucks its not going to net you that much.

knnhon · March 20, 2009

First off, you do get better mpg with free flowing exhaust. I doubt it was 2mpg though. probably a combination fo some dry warmer air combines with some favorable winds.

Now as to the complete misconception that GM would put it on the truck if it helped. GM is in the business of trying to make money. They do that by offering a standard product that will appeal to the most possible people in order to generate sales all the while lasting a long time in order to generate the fewest warranty claims. In order to help this along they sometimes put cheaper products on the vehicle than they could put on it otherwise. If it was ONLY about MPG and nothing else, every single truck would have a CAI, some type of performance tune, a free flowing dual exhaust, tonneau cover, e-fans since they were invented, underdrive pulleys, MSD wires, ACCEL SuperCoils, 3.23 gears and every other product designed for mileage and power. To somehow think that GM would have done it if it worked, so if it's not on there it means it doesn't work is absurd.

And my friend you thinking that every thing you just listed there will net you another 1.5mpg consistantly is absurd. In years past, I would have somewhat agreed with you, but we are living in a different time now. I fully understand that it's not ALL about mileage, it is a balancing act between mileage, power, reliability and cost (for GM and the Customer).

And GM has done most of the things you listed and heavily marketed a vehicle with those upgrades. It's called the XFE. I'm not sure about everything they have added, but I know a few...3.08 gears, a six speed transmission, lower ride height, tonneau cover, CAI, low rolling resistance tires, and it seems like a few other things. They did all of this just for an advertised 1mpg gain. So you are telling me that all they had to do is put a magnaflow on it?

Free flowing exhaust will net you gains if the stock exhaust is overly restrictive. On the GMT900 trucks its not going to net you that much.

This i think goes in same category as the "Fitch gasoline enzyme" product, and the D.U.I. ign. module.... both tested by magazines, and both claiming 2 MPG! NOTTA gonna happen!... What do U guys think of the 'Black Bear' Tune-up's?

superjim · March 20, 2009

I wonder if it might also have something to do with my staying local long enough to get a few fill ups at a station that doesn't advertise 10% ethanol in their fuel. I've been on the road and stopping at Pilots and Sheetz and they both use ethanol.

Using REAL GAS vs the 10% junk, is a lot more likely than the muffler helping very much.

I have a 2006 with the 4.3.

There is a town (Waco) about 100 miles south of here where I have to go on business every once in a while. They DO NOT have Ethanol in the gas.

I always make it a point to fill up there. Not sure of the mileage gains on the truck, haven't really checked it, but it DOES RUN BETTER with the REAL GAS vs the 10% ethanol crap.

I have been doing that for the last several years since they changed all of our local gas to the 10% ethanol junk.

I have checked mileage on the Cadillac when on road trips with REAL GAS vs the 10% junk... it makes a 1 to 1.5 mpg difference on the Cadillac, PLUS it runs a lot better.

MikeInCtown · March 20, 2009

First off, you do get better mpg with free flowing exhaust. I doubt it was 2mpg though. probably a combination fo some dry warmer air combines with some favorable winds.

Now as to the complete misconception that GM would put it on the truck if it helped. GM is in the business of trying to make money. They do that by offering a standard product that will appeal to the most possible people in order to generate sales all the while lasting a long time in order to generate the fewest warranty claims. In order to help this along they sometimes put cheaper products on the vehicle than they could put on it otherwise. If it was ONLY about MPG and nothing else, every single truck would have a CAI, some type of performance tune, a free flowing dual exhaust, tonneau cover, e-fans since they were invented, underdrive pulleys, MSD wires, ACCEL SuperCoils, 3.23 gears and every other product designed for mileage and power. To somehow think that GM would have done it if it worked, so if it's not on there it means it doesn't work is absurd.

And my friend you thinking that every thing you just listed there will net you another 1.5mpg consistantly is absurd. In years past, I would have somewhat agreed with you, but we are living in a different time now. I fully understand that it's not ALL about mileage, it is a balancing act between mileage, power, reliability and cost (for GM and the Customer).

And GM has done most of the things you listed and heavily marketed a vehicle with those upgrades. It's called the XFE. I'm not sure about everything they have added, but I know a few...3.08 gears, a six speed transmission, lower ride height, tonneau cover, CAI, low rolling resistance tires, and it seems like a few other things. They did all of this just for an advertised 1mpg gain. So you are telling me that all they had to do is put a magnaflow on it?

Free flowing exhaust will net you gains if the stock exhaust is overly restrictive. On the GMT900 trucks its not going to net you that much.

Thanks for helping prove my point. How much extra is the XFE package? Stuff doesn't come one every truck now does it? Why not if it helps improve mileage?

Oh, and that advertised 1mpg gain is a gain based on multiple driving styles and averaged out among lots of miles. If you want, I'd bet you could do much better. And like I said, it (the new muffler) may net you some benefit but I doubt it was 2mpg.