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  1. #1

    Default 27.5 mpg from '05 Suburban

    Hey friends,

    I'm curious who else out there is getting the same MPGs as me. I can't be the only one. We have an '05 Chevrolet Suburban LS 1500 2wd that is all original with 123,700 miles. 5.3 V8. We bought it one year ago. Ever since we bought it we've been getting great fuel economy (in my opinion). For you skeptics, I test my mileage with a calculator, and with the onboard computer. I even verify mileage against google maps and mapquest to ensure accuracy. It's no longer an issue of whether or not it's happening. Here is what I've learned: my onboard computer is correct. Every time I check it (skeptical myself) it's dead on.

    I live in Springville Utah. When I drive on I-15, the freeway, using the cruise control, A/C on, I get the following MPGs:
    60mph = 26 + mpg
    65mph = 25 + mpg
    70mph = 23 + mpg
    75mph = 21 + mpg

    We drive up to Davis county 2-3 times per month, along with other trips North. I have been checking these numbers and it's gotten boringly consistent. We got back from a trip to Centerville 30 minutes ago, 124 miles round trip. The truck had less than a quarter tank when we left, we didn't fill up, and the low fuel light still hasn't come on. I restarted the trip AVG MPG computer for the trip. By the time we got home in the driveway it was sitting at 27.3 mpg. But while on the freeway it was steady at 27.5 mpg average. I drove 60mph, in the right lane, cruise and A/C on, family and stuff onboard.

    What else have I not included?...I put new Michelin LTX MS2 245/75 R16 tires on it last year right after we bought it. Besides that, stock.

    Anybody else seeing these numbers? I can't be alone. Click image for larger version. 

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  2. #2
    Master Mechanic SupplySgt's Avatar
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    I have to say, I am VERY impressed. I get 19 or 20 during the summer months in mine (16-17 during the winter) but mine is also over 10 years older than yours and it's over 20 years old overall and has 263k miles. I was impressed with my Grandpa's 05 Z71 getting around 20 on the highway and his has even more miles than mine. Despite my preference towards the Vortec 350, I have to say that the 5.3 is an impressive motor from my experience, even without reading your thread. I'd love to have one as a daily driver. I never thought they were capable of THAT kind of fuel mileage though. I thought the only way to even approach that was with diesel power.
    93 Suburban (Southern Slayer): TBI 350, 4L60E
    73 Z28 Camaro: L82, TKO 600

    KJ4CLI



    "...Death smiles at us all, all a man can do is smile back..."

  3. #3

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    I am a little skeptical also, but since I got my tuner and the OBD II diagnostic tools for android and I have been watching a few things, you are going to get your best fuel econ if your RPM's don't go over 1500 depending on the gear you are in, so there is something to be said for not using a lead foot

    Unfortunately most people are going to do allot of high speed acceleration or deceleration and they will be driving 65-75mph so they won't realize that high a MPG rating on their 5.3L engines. And I don't mean flooring the pedal, you don't have to do that to get your RPM's over 1500.

    They are talking about raising parts of the inner city freeways in our area to 70mph. You won't catch me going 60mph when that happens.

  4. #4

    Default

    Quote Originally Posted by PantheraUncia View Post
    I am a little skeptical also, but since I got my tuner and the OBD II diagnostic tools for android and I have been watching a few things, you are going to get your best fuel econ if your RPM's don't go over 1500 depending on the gear you are in, so there is something to be said for not using a lead foot

    Unfortunately most people are going to do allot of high speed acceleration or deceleration and they will be driving 65-75mph so they won't realize that high a MPG rating on their 5.3L engines. And I don't mean flooring the pedal, you don't have to do that to get your RPM's over 1500.

    They are talking about raising parts of the inner city freeways in our area to 70mph. You won't catch me going 60mph when that happens.
    I've paid attention too, and even the smallest increase in throttle application makes a BIG difference. This tells me that a heavier truck, or larger/heavier tires, or 4wd powertrain drag, all would decrease dramatically my MPGs. Starts and stops too. I just drive it really nice, and try to be courteous to other drivers by staying right. But where I used to speed everywhere I went, now I drive nice and it makes ALL the difference in my truck. I should add that in town, with a whole month of my wife just driving 8 blocks and dropping the kids off at school, going to the library, shopping, the average will be 15.5mpg-18 mpg. Often around 18. 15.5 mpg is the worst we've seen. She drives really nice too.

    - - - Updated - - -

    Quote Originally Posted by SupplySgt View Post
    I have to say, I am VERY impressed. I get 19 or 20 during the summer months in mine (16-17 during the winter) but mine is also over 10 years older than yours and it's over 20 years old overall and has 263k miles. I was impressed with my Grandpa's 05 Z71 getting around 20 on the highway and his has even more miles than mine. Despite my preference towards the Vortec 350, I have to say that the 5.3 is an impressive motor from my experience, even without reading your thread. I'd love to have one as a daily driver. I never thought they were capable of THAT kind of fuel mileage though. I thought the only way to even approach that was with diesel power.
    Thanks for the reply. I love those old TBI motors. My '96 C1500 GMC Sierra, 2wd, 5-speed, 5.0 TBI V8 would do 20 mpg if I tried hard. I love how simple and sturdy those motors are. But, I AM impressed GM can get 100 more horsepower AND better fuel economy out of this 5.3 Vortec. At least in my case.

    On our trip to Arizona (10 hours) this past Thanksgiving we averaged around 21 mpg for the entire trip. I was very pleased, considering my friends with their minivans boast 21-23 mpg on their trips. I'm not anti-minivan, but I love my '05 suburban. We drove our old TBI '88 till it had...280K miles on the original motor. Good truck.

    I really think the 2wd, and tires make the difference on mine.

  5. #5

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    Those are numbers I will NEVER see in my truck! The main reason is my driving style. I don't drag race from stop light to stop light but I do rapidly excel. And 60 mph? Not likely. Although as I have gotten older I have slowed down a lot.





    2011 GMC Sierra SLE - 5.3 - 4X4 - Z71 - King Shock Level Kit - Body Color GMC grill emblem - 2 Tone Engine Cover, Rad Cover and Battery Box - Volant CAI - Tru Cool 40K tranny cooler - Sylvania ZXE bulbs Hi/Low -TriFold Hard Tonneau Cover- CoverCraft Seat Covers - Diablo inTune - GoRecon LED under rail lights - GoRecon LED White Lightning Tailgate Light Bar - Windows tinted to 45%- Kenwood DNX6990 - JL Audio C5-650 &650X- JL Audio Amp- Interco Truxus M/T 33x12.50x18

  6. #6

    Default

    Part of it has to do with atmospheric pressure, air density, etc. People on the west coast, east coast, etc will not have the same experience taking that into consideration also.

  7. #7

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    Quote Originally Posted by PantheraUncia View Post
    Part of it has to do with atmospheric pressure, air density, etc. People on the west coast, east coast, etc will not have the same experience taking that into consideration also.
    Good point. I remember when I lived in Arizona, and lived above 5000 ft (White moutains area), our vehicles were more powerful when we went down to Mesa/Phoenix and ran much stronger because of the denser air. I assumed they would achieve even better mileage in that scenario, but I could be wrong. I have never taken humidity into account.

    One more thing, my 2005 Suburban has no trailer package. I can tell it did at some point, but for now I just tow using the a ball hitch I put on the bumper. It's plenty strong for my light loads (single axle trailer with quads). I'm assuming I'm running even lighter without that additional steel bolted beneath it.

  8. #8
    Master Mechanic SupplySgt's Avatar
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    Quote Originally Posted by chrisreed82 View Post
    Thanks for the reply. I love those old TBI motors. My '96 C1500 GMC Sierra, 2wd, 5-speed, 5.0 TBI V8 would do 20 mpg if I tried hard. I love how simple and sturdy those motors are. But, I AM impressed GM can get 100 more horsepower AND better fuel economy out of this 5.3 Vortec. At least in my case.

    On our trip to Arizona (10 hours) this past Thanksgiving we averaged around 21 mpg for the entire trip. I was very pleased, considering my friends with their minivans boast 21-23 mpg on their trips. I'm not anti-minivan, but I love my '05 suburban. We drove our old TBI '88 till it had...280K miles on the original motor. Good truck.

    I really think the 2wd, and tires make the difference on mine.
    If you had a 96 it would be a Vortec. Used to have a 96 GMC Sierra (never should have gotten rid of that truck) that I averaged around 20 with when I stayed out of the gas. The actual TBI motors (from 87-95) are gutless turds IMO. That's what I have in mine. I'm pretty sure your Vortec 305 would feel more lively. Don't get me wrong, it gets me from point A to point B reliably, but when it comes time to move it's going to make pulling a trailer with my stuff absolutely miserable. It will be even more miserable when it comes time to pull my Camaro. When I do move, it will be back home to Oklahoma most likely. I'm hoping my Grandparents will be able to let me borrow their 05 when it comes time to pull all that stuff home (unless I've been able to swap in a new motor by then). If not, it will be a miserable 700 miles to drive.

    I would expect to get better fuel mileage in the winter when the air is more dense, but now that I think about it, the ECM adds less fuel when it senses less air (and the less dense air pulls less fuel through the venturi in the carb on my Camaro), which would explain the better fuel mileage when it's warmer out.

  9. #9

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    Thats great mileage for a Suburban. I've seen a few others get mileage like that if they keep their foot out of the throttle.
    My wife used to be able to get 22/23 in our 96 Suburban with a 7.4, I couldnt ever get over 16, but she drives a lot different than I do.
    Your final gear ratio has a lot to do with the numbers vs speed your getting also.

  10. #10

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    Quote Originally Posted by SupplySgt View Post
    If you had a 96 it would be a Vortec. Used to have a 96 GMC Sierra (never should have gotten rid of that truck) that I averaged around 20 with when I stayed out of the gas. The actual TBI motors (from 87-95) are gutless turds IMO. That's what I have in mine. I'm pretty sure your Vortec 305 would feel more lively. Don't get me wrong, it gets me from point A to point B reliably, but when it comes time to move it's going to make pulling a trailer with my stuff absolutely miserable. It will be even more miserable when it comes time to pull my Camaro. When I do move, it will be back home to Oklahoma most likely. I'm hoping my Grandparents will be able to let me borrow their 05 when it comes time to pull all that stuff home (unless I've been able to swap in a new motor by then). If not, it will be a miserable 700 miles to drive.

    I would expect to get better fuel mileage in the winter when the air is more dense, but now that I think about it, the ECM adds less fuel when it senses less air (and the less dense air pulls less fuel through the venturi in the carb on my Camaro), which would explain the better fuel mileage when it's warmer out.
    Yeah, it was a '95. You're right. It had the transition dash on it with the upgraded interior, but only one airbag and cup holders on the passenger side. It was definitely the TBI 305. It had good power for everything we did with it, but by today's standards it was weak. I'm old school, so I didn't mind gearing down while going up hills pulling. I frequently hit 3rd pulling a grade with the bed and trailer loaded. What year is your Camaro?

    - - - Updated - - -

    Quote Originally Posted by tbplus10 View Post
    Thats great mileage for a Suburban. I've seen a few others get mileage like that if they keep their foot out of the throttle.
    My wife used to be able to get 22/23 in our 96 Suburban with a 7.4, I couldnt ever get over 16, but she drives a lot different than I do.
    Your final gear ratio has a lot to do with the numbers vs speed your getting also.
    I'm sure you're right. As far as I can tell, mine has the 3.42 rear end. I have found my suburban will get up to speed with very little throttle application if I'm just patient. 22/23 out of a 454!? That's incredible. I love those old big blocks, and almost bought one before we found this '05.

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