I just bought some longtube headers for my 2012 4.8l, already have a air aid CAI as well. I was wondering if those of you with bigger tires have done the longtubes and or tune and if you got your mpg and power feel back. You would think that mathematically the more power at lower rpms from headers would cancel out larger tires (I'm thinking 285s). Not sure if this works into real life.
Long tube headers MPG with bigger tires
- Thread starter Matte454
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My 4.8 has a Blackbear tune. Helped a lot on low end and shifting. I'm still getting 17.5 MPG avg after 25,000 miles. Pretty much all you can expect realistically if you don't drive it hard. Long tubes should help low end and midrange a little, but they won't improve mileage,
Get a Black Bear tune with that CAI and headers then power will not be a problem. MPG on the other hand in theory will be improved, but this is assuming you don't use that improved power and sound of the headers.
The headers will increase the sound in and out side of the truck. Don't forget, you will have to figure out something to do with your cats when you put those headers on assuming you live in a state with inspections.
The headers will increase the sound in and out side of the truck. Don't forget, you will have to figure out something to do with your cats when you put those headers on assuming you live in a state with inspections.
Still deciding on the cats. I'm in Canada so no emissions testing needed but I am not ready for a tune yet. I want the ability to put the truck back to stock for warranty (no magnussen moss warranty act in Canada) and I was explicitly told not to put a tune on. I may use the stockers and cut up the y pipe or just buy some cheap high flow cats. My goal is to get the power well keeping the noise down. We tow a 4500lb trailer long distances and the truck is either going to work at 4am with me or to school with my wife.
Not going to happen, my friend. I am not sure what you are towing, but even the 5.3 and 6.0 are not known for their mileage when towing. 4th gear is a dream, except on flat ground at 55-60 mph.
I have towed with the 5.3 and 6.0 for thousands of miles, and the RPM range required to do so means poor mileage, unfortunately, even with the very mods you mention.
My son has a 2002 RCSB that we put ARH Long tubes on, and a Blackbear Tune on his 5.3. Pretty snappy little combination. As soon as we hooked a 2500 pound trailer to it, and went 300 miles, the mileage was 8 MPG.
I have tried in several other scenarios, as well.
onac255
Bitch You Ain't No Nerd?!?!?!?!?...
09chevyAV
I'm NEW... What now?
Going up to 285 isnt really that big of a jump. I know that stock I had 265/70R17, currently I have 285/70R17 and it didnt do that much. The tire is only about 1.5 inches taller and doesnt throw the speedo more than 1-2 mph.
Cowboy Cadillac
Ain't no trash in my trailer!
If you want better milage put in higher( numerically lower ex.3:42) gears if you want better towing abilty go to a lower ( numerically higher ex 4:10) gear. If your towing lots with the 4.8 I'd get lower gears to make it easier and suffer the mpg loss of in town driving.
09chevyAV
I'm NEW... What now?
Thats a very good point man. But dont go too low or that will defeat the purpose of getting better gas mileage because it would go down. Stock on my avalanche is 3.08 gears. Like what the F*&K is that?!?!?!? 
I think it should come standard with 3.42 and have an upgrade of 3.73 for the tow package personally. Or maybe even 4.10s. I know when I put my lift and tires on I am going with 4.10 or 4.56 for some 35s
I think it should come standard with 3.42 and have an upgrade of 3.73 for the tow package personally. Or maybe even 4.10s. I know when I put my lift and tires on I am going with 4.10 or 4.56 for some 35s
