So couple random questions and concerns; first my major concern is being able to make it to the river without having to stop for fuel! When towing I'm lucky to get 7mpg, not towing I get 10 (but I'm literally 95% side streets)... Now I could understand if I was pulling a monster boat or had a freaky big block, but it's a 350 vortex motor. Yes it is a heavy lifted 4x4 truck, but come on. Also I'm not looking. For anything crazy, if be totally happy if I could 9mpg. Additionally adding a factory replacement fuel tank is out of the question, $1200 for 4 more gallons! That's crazy.

So first thought; I current have the normal broken exhaust bolt. So my thought was while I already have the manifold off install some headers and some good high grade bolts. Now I'm not looking for any gains, and I don't really want to worry about having to deal with smogging long tubes. I was just thinking some cheapo set of shorties? Or is this just a waste of money?

Also I'm lifted and rolling some STT Cooper 35's; I'm pretty sure I'm highly under gear'd for my current application with 3.73's. Is regearing going to make that much of a difference?

And finally I have been told time and time again don't mess with the stock air box in these tucks because they are set up to pull from the best possible place already; I've also been told that the stock tube is the biggest area of restriction. They make a replacement tube assembly, but is it really worth it?


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10 MPG.   

Couple stupid ones.

Did you calibrate the speedo/odometer with the new tires?

Second, you lift a truck and put on 35's and now you are bitching about the MPG? 

My '94 Z71 4X4 extended cab towing a 21' day cruiser with a Lance 845 cab-over camper never got less than 13mpg. And that was taking it up through Oregon and Lake Shasta and everywhere in between. when I sold it it had 288,000 or so miles on it and I still see it at least three times a week on the road (the dude owns a Backflow prevention business).

There is something completely wrong with that truck IMHO.

GT

 

Not bitching about the mpg that I get, I'm more or less asking what can I do to make it to the river without having to stop for fuel... Whatever that answer is, that's what I'm looking for...

I like lifted trucks and understand the dollars it takes to run them, that is not my issue. My issue is efficiency, like you even said something has to be wrong with the truck for it to suck that much! Haha

I've also thought about taking out the spare (that will never work) and figure out how the plumb in an auxiliary tank...?


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10 MPG.   

Did you calibrate the speedo/odometer with the new tires?

GT

No I have not re-calibrated anything on this truck.

I had a thought of eventually get a custom tune done, but I'm not sure how worth it that is either.


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Not bitching about the mpg that I get, I'm more or less asking what can I do to make it to the river without having to stop for fuel... Whatever that answer is, that's what I'm looking for...

I like lifted trucks and understand the dollars it takes to run them, that is not my issue. My issue is efficiency, like you even said something has to be wrong with the truck for it to suck that much! Haha

I've also thought about taking out the spare (that will never work) and figure out how the plumb in an auxiliary tank...?


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With 35's, you should have at minimum 4.10:1 gears. Have you looked into an underdrive? You could just do the rear drive shaft.

It almost sounds like you have a plugged CAT or faulty injectors....

Have you driven it with a scope on it? I would look at the o2 signal switching and the MAP input signal.

Something is screwy..

GT

No I have not re-calibrated anything on this truck.

I had a thought of eventually get a custom tune done, but I'm not sure how worth it that is either.


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If the speedo is wrong, your actually getting closer to 13 MPG.... It came with 32 " tires... I did Crayon math, but at 60 MPH on the speedo, you are actually going 65...

GT

Sorry air raid kit.


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01 with a 350?? You sure it's not a 5.3?

My 00 Sierra 4wd with a 5.3 on 32s gets 12ish when towing. The stock manifolds on these ls motors flow really well, so I would say don't waste ur time or money on headers, u won't see a difference.

As far as the intake goes, you are 100% correct. I would run the stock box and an air-raid intake tube, I've seen tests that show that's the best setup.

Also I'm sure those 35s with stock gears are definitely not helping matters. Gearing will for sure help, but remember you will have to gear both front and rear the same.


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01 with a 350?? You sure it's not a 5.3?

My 00 Sierra 4wd with a 5.3 on 32s gets 12ish when towing. The stock manifolds on these ls motors flow really well, so I would say don't waste ur time or money on headers, u won't see a difference.

As far as the intake goes, you are 100% correct. I would run the stock box and an air-raid intake tube, I've seen tests that show that's the best setup.

Also I'm sure those 35s with stock gears are definitely not helping matters. Gearing will for sure help, but remember you will have to gear both front and rear the same.


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It is a 5.3...? I thought that was a 350?

That is basically what I've heard also, one of my cousins is an engineer and works for Spectra and he even said don't waste the money on their intake.

Gears, yeah I have a mechanic at my work that does gears on the side. He said he would do my truck front and rear with a posi lock for $1000.


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youd have to take it in...or to some one with a tool that can talk to the computer.  not of the code reader variety.
an under drive is like another set of gears...which are usually lower... in a case that attaches to the end of your trans.  this again would help get you closer to the optimal road speed to engine speed ratio.
an engine tune may free up a few ponies....maybe even increase your mpg. but not if engine has issues....check engine light on?  bad o2 sensor will kill mileage.   re-calibrating speedo....doesnt increase anything.  just adjusts or calibrates your speedo to work with your bigger tires.  larger tires spin slower so they read slower.  keeps everything closer to factory specs, shift points, etc.  youll need a device to plug in to calibrate, i think....
i would start with simple stuff....cheap or free stuff first.  like tire pressures.  if the tire says it needs X pressure....you should be at that pressure.  too low and mileage goes down.  tires on trailer?  brakes dragging on trailer?  clean air filter on truck?  i never noticed an impressive increase with an aftermarket intake....but, maybe your truck would respond better to one than mine.  at least a better/clean filter.  clean fuel filter?  after that....may need to hook up a device to see what your engine is doing.  if all is  well....may need to put lower gear in.  these are things id check...not definitively speaking.

also, to find mileage using your speedo (if corrected), when you fill up.... reset your trip meter to zero...when you go to fill up again or put any amount of fuel in, note the amount of gallons ...divide number of miles on trip meter by the number of gallons you put in...this will give you your actual usage.

Just talked to my dad. He has a 2000 Silverado 4X4 with a 5.3L  and has nearly 300,000 miles on it, he has a JET MAF, Borla muffler, smog legal as the day it was bought and he regularly gets 22 MPG. He said when he tows the big boat (23' triple axle trailer about 5,000lbs) he gets 14-16 depending on how white he wants to drive..

You my friend have broken chit.

GT

Just talked to my dad. He has a 2000 Silverado 4X4 with a 5.3L  and has nearly 300,000 miles on it, he has a JET MAF, Borla muffler, smog legal as the day it was bought and he regularly gets 22 MPG. He said when he tows the big boat (23' triple axle trailer about 5,000lbs) he gets 14-16 depending on how white he wants to drive..

You my friend have broken chit.

GT

Sweet... So that is possibly something wrong. Well that's better than having to just deal with, I can work in chasing down a problem! Makes me feel good and bad all rolled into one.


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leave your stock air intake alone if you're worried about your mpg.  more air = needs more gas. 

if you REALLY want to know what your car is doing get one of these:



its called an "ultra gauge" and it costs about $60.  it plugs into your vehicles ODBII port and it will give you EVERY detail about your car.  maf, throttle position, o2 sensor readings, fuel trims, cam advance, timing, spark, etc.  you'll know exactly why you're burning excess fuel.