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Chevy Silverado and GMC Sierra Real World MPG Numbers



  • Though I'm thrilled you're apparently getting yours to actually go into V4 mode above 62, saying what I said is a lie is completely irresponsible. I drove 900 miles round trip to buy a new Sierra based on believing that AFM worked as advertised. The fact is that both going out and coming back on a LONG test drive with cruise control set to 68MPH, the truck never once entered V4 mode and I was getting instantaneous mileage between 13-19. You can't blame a lead foot when the cruise is set to 68 and you can't blame hills or the wind when it does it both directions. As I backed the cruise control down, when I would hit about 62MPH the truck would start to very intermittently go in and out of V4 and below 60 would go in and out frequently. That IS what happened. Period. What possible motive would I have to lie? That is after all the reason the new Sierra remained on the lot and the wife and I returned home in our Canyon. I thought others should know for those that think believable gas mileage is as important part of a new vehicle purchase as I do and maybe just maybe this technology has a few holes in it yet since others are complaining about horrible mileage too. I'll keep driving my Canyon in the meantime that actually hits and sometimes exceeds its MPG rating. Just got 23.5 on a trip to/from Colorado in it @70MPH and it's only rated at 22 HW.
  • I am very impressed with the mpg on my 2007 4x4 crew cab z71 w/6.0 L engine. On a 350 mi. trip shortly after I bought the truck I got 18.2 mpg overall. This is before the engine was even broken in. On another note the on-board computer is very accurate. It showed 18.2, and I calculated 18.2 based on my fill-up.

    The truck frequently goes into afm mode below 70 mph, and occasionally between 70-75 mph. 74-75 mph seems to be the cutoff where the afm won't engage any more. I think it would easily meet (or exceed) the 19 mpg highway rating if I stayed at 65. BTW my trip was mostly in cruise control. That is key to getting good mpg. The trip also included about 10% mountain driving, but it is interstate thru those mtns. and the speeds were about 70 mph.

    In lousy stop-n-go Los Angeles traffic I get 14-15, which is as good as I can expect.

    AFM really works. As long as it is reliable, I am sold on it.

    I recently bought a pop-up trailer, approx. 2400 lbs. empty. I am curious what my mpg will be while towing. Will post when I have some data.

  • 1offroader, I'm getting good results too - I got an 07 Crew Cab MAX with 4:10 gearing, but I lifted it 3" and put on 33"s so I'm at about 3.85 effective ratio. Still, I got 17 mpg on a recent 600 mile trip which included a lot of "hammer time" passing RV's, mountain passes, hills, etc. I think I could have squeaked out 18 if I had been gentle. I'm getting about 14-15 in town easy driving.

    The bottom line is that there will always be some flat driving, downhill time, tail winds, etc where the AFM will engage and save fuel. I've actually seen it engage while pulling my 5000# Camper. There will also be times when you'll never see AFM engage - High speed highway driving, hot day - AC running all the time, head wind etc. Still, I'm sold on the technology.

    One potential problem is that the system does not rotate the cylinders that it disengages... i.e. the same 4 cylinders always turn off. Over time, will the uneven wear cause problems? With the tight tolerances and better materials used in these new engines, it may never be an issue, but my instincts lead me to believe that it could be.... Time will tell
  • summit

    The issue of uneven cylinder wear should not be a problem. The pistons in those cylinders are still moving up and down - they have to, they're connected to the crank shaft. They just aren't drawing in fuel and firing because the valves are de-activated. I wouldn't worry about uneven wear, that's not going to be a problem IMO.

  • You're probably right... I was thinking more in terms of uneven carbon depositing on the valves, seats, injectors etc. Still, things are made so tightly today that it's probably not an issue at all. I love my new Silverado!

  • I am thinking about putting a tonneau cover on my 07 new body style silverado ext cab. I am interested in a tri-fold but I am worried that the black plastic on the tailgate will interfere with the cover. Does anyone have any suggestions on types of covers or if this would be a problem. Thanks for the info.
  • If your getting lousy mpg and your buddy is not check to see which 5.3 you have? The aluminum block will get the lower millage than the cast iron block in my experience.
    My aluminum block with 310 hp gets average of 14.1 while my cast iron block 290hp will get 18mpg average and up to 21 mpg on the highway at 70 mph.
  • z15z15 Posts: 2
    I have an 08 Sierra 4x4 SLT Z71 E-Cab iron block 5.3

    I have seen mine go into 4 cyl mode about 65 mph while on cruise control. If you are not on cruise control any pressure on the pedal will not allow it the select the V4 mode. If the rpm goes up 1 it will kick into V8.

    About 5,000 mile on my truck. I was avg 18.3 mph till the winter weather hit and its dropped to about 17.6 but I have it in AUTO 4x4 mode all the time, snowing for 2 weeks straight and roads are mostly snow covered or slippery.

    A recent 500 miles trip I average 19.7 mpg on relatively flat county on cruise control at 65mph. Coming back I was carrying about 700 lbs of cargo. I also changed all the lubricants in my truck to synthetic, the engine, both axles and the transmission.
  • I'm in the market for a new Sierra/Silverado. I currently have a 06 1500HD Crew 2WD. Happy with the power, but getting 11MPG. Would like to get 4WD and improve the MPG from the 11. The 1500 with 5.3/3.73 with AFM would probably fit most of my needs. However, there are a few times I probably would be better off with a 3/4 or one ton. Question is what are you guys getting with the 6.0 and new 6 spd in the HD. As stated above, the 5.3 would probably fit the needs, but if the current 6.0 with the 6 spd is getting over 15 regularly, I'd prefer that setup. I see GM has the 6.0 with the AFM in the 1500 series. Is the AFM coming to 2500/3500 or is that just silly?
  • Well, I have the 5.3 on my "new" chevy 1500 2wd extended cab that is supposed to have the AFM. Ive put 22,000 miles on it since memorial day and have yet to achieve anything better than 18-19 (19 on a good day) MPG. BTW, the sticker said 22 hiway.

    My question for those who know, is if you have the truck without the DIC buttons, how would you know if AFM is active or not? The book says there is a display regardless of whether you have the DIC buttons or not, but fails to mention how one would know.

    I drive many days from gas station to gas station only touching the brake pedal and ignition when I leave the first station, stopping at the next one. 60-65 mph, cruise on, all highway. I drove 948 miles this week and might have achieved 18 mpg if I rounded it up. I generally get about 400 - 420 miles per tank and my fill ups are between 22.5 - 24.5 gallons. My simple math tells me that if I were to get even 20mpg, I should go 440 miles on 22 gallons of gas.

    No, I dont see any indication that AFM even exists. The serial number says it has it, the sticker says it has it, but other than that, there is no indication that it exsists or if it does, that it functions. Ive even driven 2 tank fulls with the trailer button depressed only to find the same exact milage.

    I love the truck, dont get me wrong. It's not the most comfortable for 6 or 8 straight hours, but it's a truck. My question remains. How would one know when the engine goes to 4 cyl. My next question (assuming there is no way for joe truck owner to know) is how would the dealership test it? Can they hook a computer up to it and see it function, can they engage the EFI manually or however AFM works? How can they show me that it is doing what it says it is or for that matter, even show me that it's installed?

    18 is ok? Thats 20% off the sticker. What if your wife was in the grocery store, bought $100 worth of groceries, and the store constantly failed to load more than 80% of those groceries in her trunk? What if you bought an air conditioner rated at 16 SEER only to find out it was a 13 SEER? What if the fuel stations only delivered 80% of the fuel the pump said it did?

    All I want to know is... Is it there, and if so, does it work (show me). It's a shame a coworker who has the same truck except his is 4wd and he gets over 20 per gallon with the same monthly miles and same type of driving.
  • fueledupfueledup Posts: 64
    about ready to purchase an 08' silverado 1500 ltz extended cab 8 foot bed 4X2 with 3.43 rear end. truck is loaded including nav. msrp $36,915, selling price $32,500 + tags, tax, and title. with 0%-60month financing. is this a good price and can I expect mileage as advertized. any advise welcomed.
  • bkerchakbkerchak Posts: 9
    I have an 07 1500 extended cab work truck with 6 1/2 foot bed 4x2 with the 3.23 rear end and locking rear diff and the 4.8 was advertised at 16/20 and I get right around 14/19......I run 87 octane with a tonneau cover... I only have 9,400 miles on the engine so I hope the numbers will improve slightly....I am thinking of adding a K and N air filter to help improve mpg......not bad for a v-8 that puts out 295 horse power and a truck that has a curb weight of 5,400 pounds...
  • the_big_althe_big_al Posts: 1,079
    I'm a little late to the party but... I have a 4.3, albiet in an S-10 and I have gotten as high as 24 on the highway, but usually about 22. City driving is between 16-18, depending on how you drive. I would assume that for a full size which is much larger and more wieght than the S-10, the mileage numbers would be significantly lower...
  • xscoutxscout Posts: 141
    After looking at the EPA mileage estimates, it looks like a Ram 1500 3.7 with manual gets about the same mileage as a Chevy 1500 4.3 manual, Dakota 3.7 manual, and Ford Ranger 3.0 and 4.0 manual. Is this really accurate considering the size and weight differences between these trucks?
  • obyoneobyone Posts: 8,054
    Yeah the ranger sucks.
  • I have an '07 Silverado 4X4 Z71 with the 6.0L engine, 3.73 locking diff and live in Colorado. I am able to consistently get between 18 and 21 mpg with a combination of hilly and mountainous driving. I couldn't be more happy with it. As for the AFM, I can't tell when the truck is running in V4 or V8 mode except to look at the readout on the dashboard. Driving across Nebraska I consistently average 20 mpg in the flat country. In the hilly midwest near the Great Lakes, I'm lucky to get 17 or 18 mpg. In all cases, I drive between 65 and 70 as the law allows. As for trailering ... get the 4:10 axle. I didn't and I'm very disappointed in both performance and mpg ... usually between 8 and 10 mpg.
  • Currently 43,500 miles on the truck. Daily NJ driver. Average MPG since new is 19.7. Getting consistently above 20MPG in the warm months, and 18-19 in Jan-Feb.
  • dad00dad00 Posts: 3
    Hi all, I have just taken delivery of an 2005 Siverado 1500HD with 66,000 kilometers (40+ thousand miles). The fuel consumption is atrocious - 12mpg in imperial gallons. (6L & 3:73 diff). Someone told me to check the thermostat as if it opens to early, at to low a temperature, the transmission will never go into "final stage" or overdrive and the diff won't lock causing slipage and higher rpms and fuel consumption. I have never heard of this. Is it a possibility?
  • jrzdvljrzdvl Posts: 5
    I have an 07 Sierra 5.3 4X4 with the 3.73 rear. To the guy wondering about AFM, I can tell when mine is in 4 cyl by the sound. The exhaust make a slight fluttering sound in 4 cyl (flat and level road) compared to the steady sound of the 8. You have to pay attention though. Like some others, I was also getting over 19 in warmer weather but it has dropped down now to about 17. (about 9000 mi on truck) That 3.73 hurts but it was not opotional. One thing I would suggest is Mobile One. I switched to that oil at about 3000 and saw an immediate jump of about 1 mile per, provable because I keep track of every drop of gas that goes in. I have switched to K&N filters in other trucks and cars and never noticed a thing in normal driving. Keep the tire pressure up, though
  • I'm currently shopping for a used (maybe a few years old) Sierra or Silverado. Does anyone know what year the 5.3 was available in these trucks of the top of their head? Thanks.
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