Fuel mileage

[SMalafy]

I previously had a 95 12 valve which gave me 21 MPG on the highway but the frame rotted out on it. I went and found a rust free 2001 24 valve but only get 18 MPG. Both trucks have the same rear gear ratio 3.56 and both auto's. Does the 24 valve burn more fuel than a 12 ?

 

[bcbender]

That is my understanding but have never owned one, more power / more fuel

 

[BigPapa]

Yes, sounds normal.

 

[SMalafy]

That is my understanding but have never owned one, more power / more fuel

When I owned the 12 valve I had a #5 fuel plate in it too. It had more power than this 24 valve with the fuel plate but still got 21 mpg

 

[GAmes]

In the grand scheme of things a 24 valve will give you better mileage than a 12 valve because the fuel and timing is computer controlled. There are more than a dozen factors that affect fuel mileage besides gearing. One of them is memory.

 

[SMalafy]

In the grand scheme of things a 24 valve will give you better mileage than a 12 valve because the fuel and timing is computer controlled. There are more than a dozen factors that affect fuel mileage besides gearing. One of them is memory.

So are you saying I should be getting the 21 mpg or better ? I wonder where I should be looking then.

 

[GAmes]

So are you saying I should be getting the 21 mpg or better ? I wonder where I should be looking then.

Yes, IF (and that is a big IF), all other parameters (weight, speed, traffic, altitude, temperature, wind, external accessories, tire size, tire tread pattern, brake adjustment, alignment, vehicle height, bumper spoiler, etc.) are the same and you honestly got 21 mpg.

 

[SAndreasen]

I previously had a 95 12 valve which gave me 21 MPG on the highway but the frame rotted out on it. I went and found a rust free 2001 24 valve but only get 18 MPG. Both trucks have the same rear gear ratio 3.56 and both auto's. Does the 24 valve burn more fuel than a 12 ?

I’ve owned 3 twelve valves and 5 24 valves never had anything get over 18.5 the 12 valves did a bit better I don’t know why.. I’ve heard of guys getting 21 but never seen it

 

[GAmes]

I once drove I10 from San Bernadino to Junction, TX at 57 mph, no trailer and time on my hands. I averaged 22mpg. Driving 65 I get 18.

 

[BigPapa]

I’ve never known a 24-valve to get better mileage consistently than a 12-valve. When I was driving 50 miles to work through the backwoods, 55 mph max, my ‘95 RWD RC 5-speed got 25 mpg average on four tanks one spring. On my most recent 30 mile commute, a mix of 15 miles 55 mph max and 15 miles of interstate, with the auto this time, it averaged 19-21 mpg.

 

[SMalafy]

Yes, IF (and that is a big IF), all other parameters (weight, speed, traffic, altitude, temperature, wind, external accessories, tire size, tire tread pattern, brake adjustment, alignment, vehicle height, bumper spoiler, etc.) are the same and you honestly got 21 mpg.

Yes I honestly got 21 and that's doing 80 mph with an empty truck bed . Before the speed shop put the fuel plate I was getting 21 and after it was the same too only a lot more power

 

[BigPapa]

My truck never liked interstate running at 70+. It’s fuel mileage sweet spot was a steady 55-60.

 

[SMalafy]

And both trucks are 4 X4 s I did buy a smarty tuner for the 24 V and the first time I programed for fuel economy I got 21 with the 24 V but now something went amiss with the tuner and I get a whole different program with lots more power but only 16 mph. Good if your towing I guess. I tried to contact the company by email through their web page and contracted malware on my PC and had to shut it down manually to get rid of the malware. I do not know how to contact them to get the issue resolved.

 

[GAmes]

Yes I honestly got 21 and that's doing 80 mph

That's your story and you are sticking to it?

 

[SMalafy]

Yepper, I can still divide numbers unlike these younger kids that need a phone or calculator

 

[brucejohnson]

Yes I honestly got 21 and that's doing 80 mph with an empty truck bed . Before the speed shop put the fuel plate I was getting 21 and after it was the same too only a lot more power

How long have you had the 2001 24v?
Manually calculated or overhead readout?
GAmes post #7 above contains variables to be considered when comparing MPG figures.
Here is an excerpt from a spreadsheet on my previous 2002 2500 for comparison to your truck showing MPG Indicated (in overhead console) vs. MPG Computed (hand calculated). Green text is computed greater than indicated and red text is computed less than indicated. The White is daily driving, and the Yellow is towing a 10,000-pound travel trailer. The 9 MPG reflects one heck of a headwind in SD.

 

[BigPapa]

That’s a lot closer than I’d have guessed it would be.

 

[petersonj]

but now something went amiss with the tuner and I get a whole different program with lots more power but only 16 mph

I think once he gets his truck to go over 20 mph, then fuel economy will improve. Maybe he needs to bump it into second gear..., okay, enough of that.

By far, my best fuel economy is always around the 55 mph range. Using secondary roads most of the time gives great fuel economy. Freeway, not so good - especially above 65 mph.

- John

 

[brucejohnson]

That’s a lot closer than I’d have guessed it would be.

A lot better than the lie-o-meter in my 2020 6.7. Add the right column to the left column to get the displayed MPG.
The under 20 MPG figures had a regeneration included on a top-off of 7 or 8 gallons fill prior to a longer trip.
While the displayed MPG is significantly off from the hand calculated MPG, the average is better than the 02. So are the power and torque significantly better with the 6.7.

 

[SMalafy]

How long have you had the 2001 24v?
Manually calculated or overhead readout?
GAmes post #7 above contains variables to be considered when comparing MPG figures.
Here is an excerpt from a spreadsheet on my previous 2002 2500 for comparison to your truck showing MPG Indicated (in overhead console) vs. MPG Computed (hand calculated). Green text is computed greater than indicated and red text is computed less than indicated. The White is daily driving, and the Yellow is towing a 10,000-pound travel trailer. The 9 MPG reflects one heck of a headwind in SD.

View attachment 139442

I have had the truck for 4 years now and it was manually calculated using the trip odometer and the fill up gallons at the end of a trip.