Re: Special Economy Truck?
 

With a 305??? how?

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!

Re: Special Economy Truck?
 

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.

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.

Re: Special Economy Truck?
 

That's about the time people started rolling their eyes at EPA estimates.

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.

Re: Special Economy Truck?
 

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

Re: Special Economy Truck?
 

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.

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.

Re: Special Economy Truck?
 

Driving over a cliff....:lol: