Fuel mileage

[Agnem]

2000 RPM @ 60 MPH is not 4.10's. That's a 3.55 you got. For really great mileage, get down closer to the torque peak. The Moosestang, with 3.08 rear and a ZF5, turns around 1600 at 55 MPH, and gets 23 MPG.

 

[madpogue]

2000 RPM @ 60 MPH is not 4.10's. That's a 3.55 you got.

That actually does sound right for 4.10s. With 3.55s, at 2000 RPM you should be between 65 and 70 MPH.

For really great mileage, get down closer to the torque peak. The Moosestang, with 3.08 rear and a ZF5, turns around 1600 at 55 MPH, and gets 23 MPG.

Hmm, that seems fast for 3.08s. I get aprx. 1500-1600 at 55, ZF5-42 and 3.55s in our PSDs. I would kill to have 3.08s in the IDI Batmobile, to make up for the 1:1 top gear of the T19B (actually, the old wide-ratio T19A with 3.08s would be the ideal). Did they ever even make 3.08 gearing for the front?

 

[mjs2011]

That actually does sound right for 4.10s. With 3.55s, at 2000 RPM you should be between 65 and 70 MPH.

Sounds right to me too. With 4.10, I ran around 65 at 2200 rpm I believe, now with the 3.55, at 65, I'm at 1800 rpm. The rpm may be slightly off, but that's what memory recalls for me. Also these rpms will change with different tire sizes.


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[OLDBULL8]

With 12.5 wide tires, your gonna cut 2 to 3 MPG off.

 

[Greg5OH]

i simply REQUIRE a GV! im always wanting to slip it down another gear when im in 5th on the freeway.

 

[Greg5OH]

thats really good mileage. i try to stay at 2000 rpm with 3.55s and 31" tires. i do have big west coast truck mirrors and a visor which im sure doesnt help, and im betting my pop pressure is lower than it should be.
yes im jelous of your mileage lol.

At 60mph, I'm getting about 20mpg at around 2100RPM.
At 65mph, I'm getting about 17mpg at around 2200RPM.
At 70mph, I'm getting under 15mpg at around 2400RPM.
I don't stomp on it, I let it smoothly upshift, it rarely gets above 2500RPM, and I live in the right lane.
Around 95% of my driving is highway driving, half is nighttime, and half is off-peak so I'm not clogging the roads.

1991 F250 E4OD 4.10 NA

 

[prepowerstroke]

Ik it doesn't help much when I running 70-75 at about 2,300 rpms and I start pulling a grade so I press the gas down some to keep the speed and I look out my mirror and it's rolling black smoke and it's not even full throttle lol


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[madpogue]

Also these rpms will change with different tire sizes.

No, they won't. Not unless you recalibrate the PSOM for the tire size. Or if you measure via GPS or mile markers. But changing tire size does not affect the relationship between speed and RPM as shown on the dash.

 

[mjs2011]

No, they won't. Not unless you recalibrate the PSOM for the tire size. Or if you measure via GPS or mile markers. But changing tire size does not affect the relationship between speed and RPM as shown on the dash.

Sure it will. On a zf5, the speed comes from the Trans. Changing to taller wheels or a different rear end will both affect the speed/rpm relationship. So the rpm will show up the same, the Trans will be turning over the same, which will make the speedometer display a certain speed, but different diameter tires will cause you to travel further or shorter for the same revolution of the transmission.


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[madpogue]

True, if you change your tire size, your ACTUAL speed will be different relative to your RPM. But the speed reported by the speedometer relative to RPM will not change.

 

[prepowerstroke]

So I got a good used set of 235/85/16 tires today and gonna mount them up and put them on my truck to see how much my 33's affect mpg


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[mu2bdriver]

thats really good mileage....

I think a lot of it has to do with not stomping on it, planning an acceleration up prolonged grades, and not worrying about the driver who screams up my rearview with high beams flashing with three open lanes to the left. I'll confirm my gearing later today or tomorrow but I'm pretty certain it's a 4.10. My RPMs are what the tach is showing and after 23 years, those numbers may be off by a little.

 

[BDOGONE]

I pulled 33x12.50s and went to a 30 1:2" 17 and guess what? Much better ride. No improved MPG with 4:10s. It prob pulls better, but still! 16-17 MPG for me.

 

[BDOGONE]

Should add it's E4OD

 

[prepowerstroke]

I pulled 33x12.50s and went to a 30 1:2" 17 and guess what? Much better ride. No improved MPG with 4:10s. It prob pulls better, but still! 16-17 MPG for me.

Is yours turned up?


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