1989 S1600 x Uhaul truck 7.3 IDI Fuel Mileage

hrsitton

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I have one of these, an old UHaul truck with a 25 foot box.

I'm getting around 10 MPG running 65 MPH on the flat with a few hills that do not pull down below 55 MPH.

Manual 5-speed tranny and carrying light to no load.

Just curious about what others may be getting with a similar setup. Don't recall seeing or finding any info on that in the past.

Thanks, Harold
 

Clb

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07-24 mpg are usually the claims for an idi here.
10 aint bad.
My search showed #'s all over the place...
Ymmv
 

Clb

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Just dumped $450
This week in fuel
Avaraged 8 mpg with 7k on the pin towing us 101
 

Old Goat

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The faster you go, the worse the mileage.
That big box is about as aerodynamic as a brick.

Slow down and you might pick up a mile or two.

Goat
 

WrenchWhore

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The faster you go, the worse the mileage.
That big box is about as aerodynamic as a brick.

Slow down and you might pick up a mile or two.

Goat
I agree. Check the tire pressure and keep it around 55 and you might see some improvement. Not sure what gears those box trucks had but I bet they are deep.
 

Old Goat

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Another thing, it is probably an auto trans, and doesn`t help on the fuel economy.
Probably a 5 something Differential?


Goat
 

WrenchWhore

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Another thing, it is probably an auto trans, and doesn`t help on the fuel economy.
Probably a 5 something Differential?


Goat
Original post says it's a 5 speed. My gut says it would be ZF5 but on a chassis that big and depending on year it might have something different like a spicer 5 speed like in this S1600 video...

If he's running a diff similar to the one is this video I can see why getting decent mileage is a challenge. I am just guessing here. More food for thought.

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Old Goat

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I read that yesterday, forgot it was a manual when posting this morning.

The above video is interesting, That body style came out in 1980. We got 2 of them around Oct 81, think they were 1900`s with the DT466 and both auto trans. Both dump trucks with plows.
had them for around 14 yrs.
Got a new one in 95 with 5spd with air shift 2 spd rear end. Last year the DT466 was mechanical Injection.
The other crew got a 96 with the computer crap, never did like it the way it drove etc....


Goat
 

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