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Gas Milage, Figure this out

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by wayne, Dec 6, 2001.

  1. wayne

    wayne 3/4 ton status

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    This is wierd. I had the truck 1 ton and lifted now for about 2 months and the other day I took a short road trip with it. I have made the same trip a couple of times before the lift and axle swap and always used a 1/4 tank of gas and this trip since the swap I used a little over an 1/8 tank. Could it be that I am actually getting better gas milage now then I was. I went from 3:42 gears and 31" tires to 4:56 gears and 35" tires. I do drive a little slower now but not not enough to make that much of a difference. So is it me or am I actually getting better milage?

    See <a target="_blank" href=http://coloradok5.com/gallery/Waynes-Toy>Project Mighty Mouse</a> here.
    <font color=blue>Wayne<font color=blue>
    <font color=blue>Happy Trails<font color=blue>
     
  2. txbartman

    txbartman 1/2 ton status

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    Well, you did change your gearing more than your tire size. Hence, your engine doesn't have to work quite as hard to move the truck. That will probably help in your gas mileage a little if you do a lot of stop and go. The other could be slowing down. Going from 70MPH to 60MPH on the highway can increase your gas mileage as much as 2-3 MPG. When you said you slowed down, was that based on your speedo? Since your gearing changed more than your tires, your speedo is no longer accurate. It will say you are going faster than you are.

    So, if you slowed form 70 to 60 (for example) on your speedo, you are probably really only doing 50 or 55. That much of a speed difference can make a huge difference. Combine that with better gearing, cooler temperatures and so forth and you could see a big difference.

    Brian
    Check out <a target="_blank" href=http://tx85gmcguy.alloffroad.com>My Jimmy</a> with all her projects!
     
  3. Goose

    Goose 1/2 ton status

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    I didn't run the numbers, but it looks like you raised your highway rpm a little, which can but your engine more into it's power band. This makes the engine work easier, even if it's turning faster, which can improve mileage.
     
  4. MudFrog

    MudFrog 1/2 ton status

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    Wayne... I noticed the same thing with mine.. I wasn't sure if it was pschological or what. I went from 3.42's and 31's to 4.10's and 33's. My gas gauge seems to stay full a little longer then it has in the past.

    89 K5 Silverado, 4", 33's, 3/4 ton axles
    <a target="_blank" href=http://mudfrog.rockcrawler.com>http://mudfrog.rockcrawler.com</a>
     
  5. wayne

    wayne 3/4 ton status

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    I know how much my speedo is off and at 60 before is now 68 on the speedo. It does seem to accelerate faster then it did which is credit to the gears.

    See <a target="_blank" href=http://coloradok5.com/gallery/Waynes-Toy>Project Mighty Mouse</a> here.
    <font color=blue>Wayne<font color=blue>
    <font color=blue>Happy Trails<font color=blue>
     
  6. ti.user

    ti.user Registered Member

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    Here is a math formula to calculate actual speedo readings after bigger tires.
    actual mph= (new tire diameter/old tire diameter)x indicated mph. example: new tire dia.=37.3, old tire dia.=32.8. if the speedo reads 60 how fast is actual?
    (37.3/32.8)x 60=68
    speedo reads 60 truck is actually going 68mph.
    this came out of 4-wheeler mag july 2001.
    hope this helps out.

    thom
     
  7. txbartman

    txbartman 1/2 ton status

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    That is assuming the previous tires were the original stock size tires. If not, the speedo was already off and you will have a tough time figuring it out. I just go a little slower than everyone else when on the highway and all is good for me!

    Brian
    Check out <a target="_blank" href=http://tx85gmcguy.alloffroad.com>My Jimmy</a> with all her projects!
     
  8. 6.2Blazer

    6.2Blazer 1/2 ton status

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    The combination of the gearing which puts the motor more in the powerband, and the reduction of speed could account for better mileage. Concerning what speeds you drive on the highway, the aerodynamic drag goes up exponentially as speed increases. For example, try walking into a 20 mph wind versus walking in a mild 5 mph breeze, there's a big difference!

    Also, no offense, but judging an increase in fuel economy by simply estimating how far the fuel gage went down isn't very accurate!
     
  9. ChevyCaGal

    ChevyCaGal 3/4 ton status

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    According to Steph's Webpage&gt;&lt;&gt;
    Suck Fumes Ford Boy
    I keep trying to lose weight, but it always finds me!
     
  10. TorkDSR

    TorkDSR 1/2 ton status

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    wow, you guys still have gas gauges? and you look at them? i would find it too depressing. although gas is 98 cents. whose your daddy?

    Tork DSR
    "look ma, i can make the dog pee white...."
    aol screen name TorkDSR
    <a target="_blank" href=http://www.torkpig.homestead.com>http://www.torkpig.homestead.com</a>
     
  11. wayne

    wayne 3/4 ton status

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    Ya I know looking at the guage is not the most accurate way to do it but knowing how much it would take to make the trip before and what it took this past weekend is a big difference. I only ever checked milage once and that was comming back from Georgia in the middle of the night running almost 80 mph through a full tank of gas and got just over 13mpg. Running the speed I was and comming up through the mountains in Virginia I did not think that was to bad.

    See <a target="_blank" href=http://coloradok5.com/gallery/Waynes-Toy>Project Mighty Mouse</a> here.
    <font color=blue>Wayne<font color=blue>
    <font color=blue>Happy Trails<font color=blue>
     

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