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Old 03-16-2012, 01:43 PM   #51
Squareforceone
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Re: Special Economy Truck?

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Originally Posted by Goldfinger View Post
I can get 26 on the interstate, but 20 in the city is near impossible.
With a 305??? how?
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Old 03-17-2012, 02:22 AM   #52
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Re: Special Economy Truck?

My dad had one of those 1/2 ton trucks and the 20-22mpg Hwy was 100% true! The truck had a 305V8,4 barrel,4 spd manual OD trans, 2.73 rear end and 205/75/R15 tires. I remember the thing was geared very high and was not a good hauler- but it flew down the highway in OD!
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Old 03-17-2012, 11:07 AM   #53
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Re: Special Economy Truck?

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The thing is, even if it were true, no one would ever believe that. I dont care what method your using to conserve fuel. You got a gas motor and a 4x4 long bed. I got $100 that says you are doing your calculations wrong cause there is no way i will believe you get better then 20 Miles Per Gallon. Especially not at 80 with the ac on. More like 17 tops is what i would believe there.
Oh,I don't believe it,either,but you better get all the fact straight before doubting someone. The fact is,he has a 6.2 diesel...check his signature.

I know one thing,I get my best mileage at 65 mph...2-3 MPG better. Once I get up to 70-75 it drops off and that's with taller tires spinning lower RPMs and on the hiway that's an advantage. I'm at about 1800 RPM and that's the sweet spot.
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Old 06-09-2021, 04:28 PM   #54
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Re: Special Economy Truck?

Interesting old thread. I ran across this ad and did a search since it indicates something called Chevy Special Economy Trucks as if it's a classification. It appears that it was just a marketing classification, haha. I wonder if there is anything at GM heritage, I might do some poking around. Would be cool to hear if anybody has uncovered what the actual specs were for the truck that generated the idea for the ad. The wording of the ad borders on the hilarious. Basically says that the highway mileage is impossible and goes on to throw GMC under the "bus", if you will.
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Old 06-10-2021, 08:46 AM   #55
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Re: Special Economy Truck?

That's about the time people started rolling their eyes at EPA estimates.
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Old 06-10-2021, 08:48 AM   #56
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Re: Special Economy Truck?

My military blazer gets 23mpg easily with mostly highway and some around town driving. 6.2, th400, np208, 32" tires and 3.08 gearing.
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Old 06-10-2021, 10:24 AM   #57
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Re: Special Economy Truck?

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Originally Posted by Honest Bob View Post
My military blazer gets 23mpg easily with mostly highway and some around town driving. 6.2, th400, np208, 32" tires and 3.08 gearing.
Your tire size choice will affect mileage more than you might think even if you've matched your speedometer drive and driven gears to the tires and axle ratio. 1" diameter difference can change the effective axle ratio by around .10
If you don't match the speedometer gears in the transfer case to the tires and axle ratio the speed and odometer reading will be off.

Play with the numbers a little in my RPM axle ratio tire size spreadsheet. It's quite enlightening.
http://www.mediafire.com/download/zk...ansferCase.zip
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Old 06-10-2021, 10:48 AM   #58
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Re: Special Economy Truck?

Quote:
Originally Posted by hatzie View Post
Your tire size choice will affect mileage more than you might think even if you've matched your speedometer drive and driven gears to the tires and axle ratio. 1" diameter difference can change the effective axle ratio by around .10
If you don't match the speedometer gears in the transfer case to the tires and axle ratio the speed and odometer reading will be off.

Play with the numbers a little in my RPM axle ratio tire size spreadsheet. It's quite enlightening.
http://www.mediafire.com/download/zk...ansferCase.zip
I've run into that issue trying to calculate mpg in my other truck, however the blazer's speedometer is surprisingly accurate according to my phone's gps.
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Old 06-10-2021, 11:16 AM   #59
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Re: Special Economy Truck?

I seriously believe that an A-833 2.73 combo would get 28mpg if kept at 55mph. 55 vs 70 made 5mpg difference on the 87. And the 23mpg was mixed driving, auto trans, functional AC (not that the 6.2 noticed it was on), 3.08's.
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