Re: what are you guys getting for mpg?
 

just took a 250 mile hiway trip. cruising about 70mpg @ 1800rpm and got 16.6mpg. still only getting approx.14mpg city even with exhaust.but it sounds so good!

Re: what are you guys getting for mpg?
 

:lol: :lol: :lol: :lol:

Thats just my personal opinion
Although I must say as many times as mine had been bounced off of the rev limiter and neutral dropped, it never tore anything up! well, that could be because of the tire scorching 200 horsepower...

Re: what are you guys getting for mpg?
 

2007 chevy colorado with the 2.9 getting about 21mpg city
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Re: what are you guys getting for mpg?
 

Wow i dont feel too bad about my 12mpg in a 89 2500 anymore....

Re: what are you guys getting for mpg?
 

i have an 08 reg cab long bed with the 5.3 a 4 speed auto and 3.73s I usally get around 17.5 mpg in the city

Re: what are you guys getting for mpg?
 

Ive got an 08 excab 4x4, 5.3, 4sp w 3;73 gears. Im a little over 118k mile on it. Ive run Amsoil synthetic in it since about 25000 miles. Have been running 10 ply 285/65-18s on it since around 48000 Put flowmasters on it at 78000. (love the sound.) on highway running 70mph I have seen a little over 18mpg. at 80 its down to about 16.9. My truck has a shell on it and i carry about 400-500 pounds of tools and equipment in it all the time. I do alot of off highway driving and it averages 14-16 mpg per tank depending how much off road is done.
I had an 04 4wd excab Silverado set up very similar to this truck doing the exact same job. I actually got a little better mileage out of the 04 on the highway (19.5 on a few tanks) but overall it wasnt alot different from the 08.
Basically, the afm hasnt shown me that its worth even mentioning on paper. I love my truck, but that is definately not a selling point for me.

Re: what are you guys getting for mpg?
 

lately, with gas as high as it is i have been driving my red tank a little easier, and last tankfull it averaged 17.4 MPG! very respectful mileage for a 4 door 4wd with a 5.3 and an 18 year old driving it!

Re: what are you guys getting for mpg?
 

Yeah my 88 C2500 looks good with its 13 mpg's:P

Re: what are you guys getting for mpg?
 

I bought an 08 Silverado with a 4.3 and sure its no powerhouse but its equal to or better than the 70 C-10 350 I use to have. Less low end of course but not by much. Compare it to a LS and it sucks but value wise its a good engine. I have yet to get a tank at 20 MPG but I am trying.
I drive in poor traffic conditions,stop and go, and regularly get 18 mpg.
If I try real hard I can get high 19's but often I just don't have the patience.
Towing, driving hard I have yet to get below 16. I'm pleased with my 4.3.

Re: what are you guys getting for mpg?
 

I had a 98 single cab swb and a 99 single cab swb with the 4.3. Loved both if them. Went to the 5.3 when I upgrade to the ex cab, but had zero complaints with the 4.3.

Re: what are you guys getting for mpg?
 

2009 GMC Sierra 1500 SLE 2wd ext cab, 5.3L/4L60E

I have a small PCM tuning business so I wrote a mild 87 octane safe computer tune and I'm averaging 23mpg of mixed city & hwy but mostly in town surface streets.

I've disabled all of the torque limiting tables, all the ignition timing retard control tables (except for knock), removed all the electronic throttle limiters and dialed back TM. I figured any time ignition timing gets retard it's wasting fuel due to reduced power output.

I've reserved the DOD until 60mph and it shuts off with more than 10% throttle. I added a couple more degrees of timing and redid the transmission shift tables with the TCC apply tables. I've drastically increased the TCC PWM % minimums so there won't be nearly as much slip allowed in the drivetrain without making the TCC feel like the trans shifted into another gear.

I modified the air box to grab air from the space in front of the wheel well. Next I'm thinking of cutting out that big OE muffler and just welding in a 18" magnaflow for sound. The straight through design should help with exhaust scavenging in an otherwise stock system too.

Re: what are you guys getting for mpg?
 

I just got the 2011, yesterday. The 100 mile trip home showed 16.2 0n the Gas mileage computer readout. This is a SWB standard cab 5.3 Sierra SLE, with a 3.42 geared rear end and 20" wheels and tires.

Re: what are you guys getting for mpg?
 

:c2::clap:This may be one of the best written posts I've read. Interesting :burnout:

Re: what are you guys getting for mpg?
 

We took a trip to Monroe LA in the Silverado this weekend and averaged 16.0 mpg.

Re: what are you guys getting for mpg?
 

I was able to squeeze 20.1 mpg out of my '08 with AFM, mixed highway and city over an average of 500 miles. I never went over 2000 rpms, coasted down hills and just generally babied it and drove like a really old person. It was a really effort though, normal driving style yields 16.7 mpg over an average of about 10K miles.

What really kills me is how long the 4 cyl mode stays on. If you even sniff the gas pedal it goes back into 8 cyl...I'd like to get a tune to make this stay on longer and adjust the timing tables, TM, etc. At first I wasn't worried about mileage, but with the above results and gas prices I'm starting to rethink that approach.

Mykk it sounds like you've had some success, do you do any mail order tuning or just local?

Re: what are you guys getting for mpg?
 

One thing to remember about MPG and vehicles of today is that those fuels are not as they were years ago, or, even 2, 3, 4 years ago. The main issue is the addition of Ethanol into the gasoline. Ethanol is grain alcohol, as E85 is. Depending on the percentage of Ethanol to gasoline, fuel mileage will get worse as the percentage of Ethanol goes up. It used to be that all grain enhanced fuels were 10 percent ethanol, and, mileage suffered to a percentage of that addition, but, just recently, the Ethanol percentage was upped by our lack luster government, from 10 to 15 percent, and that means fuel mileage goes down even more for it.

We must understand that alcohol fuels require richer fuel to air ratios, so, when we add Ethanol to gasoline, we effectively lean the fuel heat/light off burn-ability down, and that is like the older low octane fuels of the 1980's and 1990's, they required the throttle to be opened further to get the same power, and that meant more fuel usage for the amount of throttle opening. Add to this the leaner overall fuel to air mixtures built into the fuel systems of those vehicles, and mileage went south in one quick hurry.

Richening up the fuel curves for the Ethanol added fuels isn't the answer wither, all that does is make for more fuel usage. Very careful re-management of both injector duty cycles and creative ignition timing will help somewhat, but the return for the input doesn't bring the mileage all the way back. Very careful and sensible modifications to the fuel and ignition curves, modified exhaust systems and air inlet systems will help most of all, when all is done together, but individually, not much help. Also, "cooling off" engine operating temps only hurt mileage, as cooler inlet temps require more fuels, like a cold engine running on a carburetor needs a choke to operate when cold. Cooling off the engine temp cools the combustion chamber too much, and that demands richer mixtures, and loss of fuel mileage ensues.

Where I live in Northern Nevada, we just got 15 percent Ethanol doped up gasoline. We can tell the fuel mileages dropped considerably form that they were when we had only 10 percent Ethanol. My 1991 Buick park Avenue with 3.8 litre tuned port EFI V6 used to get 28 mpg on straight regular fuels, and when it went to 10 percent, mileage dropped to 21, and today, I filled up, calculated the mileage, with the new 15 percent, and it is now a whopping 16 mpg. I also daily ride a 1983 carburetted Honda GL650 V twin Silver Wing motorcycle that used to get 50 mpg with straight gas, with 10 percent, it dropped to 44 mpg, and now, with the 15 percent, down to 41/42 mpg.

Add to that the fuels are modified to make burn-ability "enhanced" for winter use and cold weather, vs summer fuels that have less volatility, and mileages are right dismal any more, even with the better EFI systems.

so, don't expect the mileage that is written on the window sticker, even if you drive with the proverbial "raw egg under your foot on the accelerator pedal", it just ain't gonna happen, because of government meddling and adverse additions to the fuels.

Re: what are you guys getting for mpg?
 

Yep, and the winter blends seem to be even worse...?

Re: what are you guys getting for mpg?
 

YES, they are, because of the 15 percent Ethanol blend now used, vs the 10 percent we used to have. Want to get really bad mileage, go to an E-85 vehicle. they get absolutely rotten fuel mileage after about 4,000 miles from brand new, from what I am led to believe from people that own them.

Re: what are you guys getting for mpg?
 

07 avalanche 5.3 4x4 flex with 104k miles. From the day I bought her brand new she never got over 15.5 mpg. I drive 40 city / 50 highway every day. Four weeks ago I decided to really watch my throttle input. No more WOT, nothing faster than 75, Easy acceleration! Mileage has gone up to 17.2! I am thinking of getting a bullydog gas tuner and maybe gain another 2-3 miles. I would be psyched if I could see 19-20!

Anybody running bullydog tuners? Anyone done any real fuel consumption comparisons?

Also thinking of new injectors and plugs since they are original!
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Re: what are you guys getting for mpg?
 

dont get the bullydog tuner. i bought one from summit and enjoyed it, but when i went to set the parking break, it broke off the little switch for the plug that goes into the obd-2 port. also, i had my truck tuned in person by blackbear performance. first, i would highly recommend them. second, when he was tuning my truck, justin told me the bullydog had retarded my timing a rediculous amount. i have also seen aproximatly 2 mpg increase with the bb tune

Re: what are you guys getting for mpg?
 

Skip the regular tuners and get a custom tune, their more expensive and if you live out in the hills like I do I have to drive 3 + hours to find one, but if I had a truck like this I would do that.

Re: what are you guys getting for mpg?
 

Wow, guys. Those numbers seem low. I keep a fuel and maintenance log. I calculate by hand in addition to checking the DIC. I average 15.6 m.p.g. around town and will get 20-20.3 on purely Interstate driving.

My truck is an ext. cab. 4x2 with the 4.8/3.23/4-spd. drivetrain. It is a 2008 LS 1/2-ton Silverado. I love it!

I will admit that I do get the best m.p.g. between 60-70 m.p.h. and don't get caught in much stop and go driving. Plus, things are pretty flat around the Tidewater area here.

Re: what are you guys getting for mpg?
 

I second the flex fuel vehicles sucking gas. My wife's tahoe gets no better than 14-15 mpg and with E-85 in it, we've seen less.

Re: what are you guys getting for mpg?
 

Have an 09 CCSB 5.3 Flex 4x4 w/3.42 gears. Took a 600 mile trip to Chicago and back running 75-80 and averaged 18.9 for the trip on summer gas - no ethanol. I also had the tires aired up within 2-3 Lbs of max preassure for that trip as well.

Day to Day running e10 get ~15 in the winter and 16.5-17 in the summer. Thats probably 60% highway. Yet to try E85 see how bad it is. This is my wifes daily driver.

Day to day driving has been really consistant over the past 40k. Overall I'm pretty impressed for something that can tow 10k by the book. Now would I put more then 7k behind there- nope and that only occasionally.

Re: what are you guys getting for mpg?
 

In my '10 crewcab half ton 4X4 3.73, auto, I'm getting around 14 - but that's "around town", including dirt roads/in and out of 4 wheel drive. I would be curious to see what the mieage would be in my '67 if you fitted it with an equally efficient drive train - in other words, I wonder how much the aerodynamics really effect the fuel mileage at these lower mpg levels.