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02'-06' Avalanche Owners....How's YOUR Gas Mileage?

I did the FM40 upgrade with dual 3" outlets almost 200000 miles ago. With a Spectra CAI my AV has been getting the gas mileage since. I never drove her long distance before the upgrades. I also run ACDelco plugs now, I have used basically everything else, along with 10mm plug wires.
With my BullyDog GT Tuner my power is increased. I Dyno out at 318hp and 423 torque. And I am only running the regular tune. The Performance tune requires running super unleaded all the time, and honestly I think the regular tune gives me better control of the powerband and the transmission doesn't work as hard. If I lived in the valley on flat ground I would use performance but in the mountains my tranny temps were getting in the 240's just driving to Fresno and back.
 
Just an update.  I changed my oil and went with Mobil 1 extended performance oil and filter.  I also changed the plugs and went with Delco iridium.  Part number 41-110.  As I mentioned, I quite babying the throttle.  I'm not dogging it, but am driving like I feel like driving.  Mileage is up to 15 so far.  That's mostly city driving and stop and go traffic on the interstate.
 
I just wanted to update.  Fuel mileage seems to have stabilized at around 15, give or take 1 or 2.  Not great, but better than the 11 is was getting.  I did a bit of research on my tires and it turns out that I had them really under inflated.  Doing the chalk test, I settled on 50 psi for the "E" load rated tires.  Handling tightened up and that vibration I was getting at highway speeds went away.

In the end the plugs, oil and air pressure put my mileage where I should be.
 
That's right around where I keep my tire pressure 45-50
 
TonyAngel said:
I just wanted to update.  Fuel mileage seems to have stabilized at around 15, give or take 1 or 2.  Not great, but better than the 11 is was getting.  I did a bit of research on my tires and it turns out that I had them really under inflated.  Doing the chalk test, I settled on 50 psi for the "E" load rated tires.  Handling tightened up and that vibration I was getting at highway speeds went away.

In the end the plugs, oil and air pressure put my mileage where I should be.

Hmmm. I have e rated tires I'll have to check the pressures again. This tank I've also decided not to creep off the line but get up to speed quicker. I did just check my air filter and maf, that entire intake is like sterile clean lol. Plugs, wires, knock sensors and harness also intake gaskets changed before I bought the truck.
 
Interesting reading and sums up what my research has found.  The general principals, if not specific data, are universal.

https://toyotires2-1524598101.netdna-ssl.com/assets/lib:toyo%20content/Application_of_Load_Inflation_Tables_20151020.pdf

In short, for me, going from the stock "P" rated tires to the "E" rated tires meant that tire pressure had to go from 35 to about 50 to maintain the same load carrying ability.

For what it's worth, the information that I came across indicated that at 40lbs or less an "E" rated tire  is severely under inflated.
 
Just did I round trip from TX to FL in my 02. 2000 miles 18.5 mpg with a avg speed of 75.
 
'02 z71 stock except for royal purple fluids. 3.73 gears. Stock tire size Michelin street tread. In a mix of 80/20 highway to city, I'm getting roughly 16.85. Very pleased. I have never checked any sensors or ever check tire pressure. I guess I could possibly squeeze 1-2 more mpg out...
 
It's turning out that what I was concerned about was true.  Although my Avy had very low miles for an '04, the truck was pretty much neglected.  I pulled the throttle body and it had gunk caked in it.  So, I cleaned it out and put two cans of Sea Foam in the tank before I filled up last night.  I haven't gotten a real read on the mileage yet, but I drove over 100 miles today (driving like I usually do without being light on the gas) and haven't burned a 1/4 tank yet.  That was hard to do before, even when I was trying to take it easy.
 
Have only 77,000 miles on mine. Stock 05 with 16 inch wheels.  Driving 800 miles RT to Seattle and back mostly freeway =
    20.38 mpg.  Calculated via -  Gallons used divided by miles driven...
 
I have always ran my tires at the max pressure on the sidewalk. My current blizzaks are a 50lbs tire. My previous BFG KO ran at 80 PSI. When I first had the tires mounted they used the door specs 35psi. My truck drove like crap. I inflated them to 80psi and the truck drives better, handles better and the mileage is way better.
Gas mileage is pretty easy to figure. Look at the tires on a Prius. They are very thin. This means less rubber on the ground so less rolling drag. Now you take a stock Avy 2wd with 265/70/16 tires. Then put on 285/70/17 tires. The mileage will suffer because you are pushing more rubber. But your handling and road manners increase. The thing to decide is how much handling and stability are you willing to give up for gas mileage.
The other thing is keeping your car tuned and driving by keeping the rpm,s below 1500 when accelerating.
My wife's 93 civic 4door has got 47mpg. But she shifts at about 1200rpm. Normal driving she manages 37-42.
 
No way I could keep the tach under 1500.  I'd get run over by a Prius.  Driving like I normally do, it usually stay at 2500 or under.  When merging, it gets whatever it takes.
 
I totally agree. I love hitting an on ramp at 5mph and flooring it until I hit 75-80 and I manage to hit 6000rpm a few times in the process. But on long trips just set the cruise at 80, which in my AV is 2150rpm. I get 18 average when I can do this for long distance like across northern Neveda on I-80. My best mileage ever was from Rock Springs Wyo to Cheyenne Wyo. 260 miles I used 10 gallons of gas. I was doing 80 with cruise. I had one hell of a tail wind.
 
TonyAngel said:
No way I could keep the tach under 1500.  I'd get run over by a Prius.  Driving like I normally do, it usually stay at 2500 or under.  When merging, it gets whatever it takes.

I love Priuses, they make for good traction.  :laugh:
 
I Usually get about 19 miles per gallon on trip. 2002 avy 66 . Has been fine tuned. Flowmaster mufflers, K and N n cold air induction. Great acceleration .  average speed on trip 70 to 75.
 
TonyAngel said:
Before I go shooting in the dark, I think I'll go with the most obvious and change the plugs.  Taking a closer look under the hood, I don't think they've been changed since new.  I only have 57K miles on it, but the idle isn't as smooth and I think it should be.  Probably do the wires too.
i have a 03 with 140k and a friend has a 03 with 200k. We both have original pugs.
I have a 06 Tahoe with 150k.
My sierra was at 160 when I did plugs, no differance. Did them and wires beacause it was running bad, come to find out fuel pump was the problem
these plugs last in theses trucks, so does the breaks
avelanche originals on front still 140k
sierra originals on front 169k now
tahoe originals on all 4 still 150k
 
After replacing my plugs, front O2 sensors, fuel filter and 8.5 mm MSD plug wires as well as two bottles of Techron, I am still getting only 13.5 range (two tanks after the parts and one tank on the Techron).  I'm beginning to think I have clogged cats and that the vibration/drone I sense at 70+ MPH isn't suspension related but rather back pressure building up.  I checked both pre and post CAT temperatures.  Driver side had a bit higher temperature at the exit while the driver side was the same or lower at the exit. (n) 
 
A little surprised about 26 mpg. My 2004 Avalanche with over 192,000 miles typically gets between 20-22 mpg at 65 mpg with a few hills but NOT on cruise control. At faster speeds, it will drop noticeably and will be down about 17 mpg at 70+ mpg. Looking at my scan gauge, the mpg drops significantly as speed goes up or even more when it downshifts going up a hill (like less than 5 mpg). The speed/mileage relationship makes sense when you recognize you are driving a big box. But it is a comfortable ride and my wife likes being up high driving on the interstates with 18-wheelers.
 
Haha! Hadn't read this thread in awhile. I don't even track the mileage in my AV anymore.

I just filled my 2000 Jetta TDI and got 40.1 MPG.  No ethonol there!
 
SO i was wondering something about gas mileage.  Now my daily commute is 45 miles one way and the speed traveled is about 55 to about 65 most of the trip.  The Avy hasn't been on a highway for almost a year.  When I bought the truck, the trip home was 70 mph and looked like about 17mpg.  Recently I went down the highway and mileage went straight to about 13mpg.  Now my question is:  Does the computer try to stick to your normal driving habit so much that when attempting to drive at a faster speed the mileage goes down.  And how long does it take to reset the parameters to allow the truck to get the 17 or better mpg at 70 mph again?  I get anywhere from 16 mpg to 19 mpg currently traveling at an average speed of 55mpg. Any ideas? No i don't have a check engine light on.
 
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