Well I just got back today from Dallas. This raod trip I kept the speed down between 75-80 using the cruise control 95% of the time. I got 17.69 mpg. As in my first post on this thread I got 15.6mpg with the cruise set @85mph. Thats a 2.09mpg difference slowing down 5-10 mph. Both trips were not loaded. But the weather sure was horrible with all the rain. Maybe the wet truck helped the air move across the truck a little easier. I guess to get around 20mpg I gotta slow it down to around 65-70 mph but that will never happen flying down these Texas highways. Sure wish I was still on the original flash the truck came with.

 

Question: Would it be reasonable to expect a 6.0 4x4 and a non-4x4 Dually to get the same mileage under same driver / conditions etc..?

Or what should the difference in milege be between a reg cab 6.0 2WD and CC longbed 4x4 or a Dually 4x4?

Is the gearing different? Certainly the weight is but is standing curb weight much of a factor on these Beasts?

Just wondering?

 

F350, Crewcab, DRW, 6.0L, 4.10 L/S, built 03/04, getting 10.5-12 (calc'd) towing 35ft 5th wheel (12,000+ lbs) & 17-18 (calc'd) highway.

 

Kw I just finished testing all that you have asked about. Poor sales person about went crazy. We drove a 3/4t SC 2WD and checked for RPMS (3:73 rear), we then drove a dually (4:10 rear) and there were 300-500 rpm differences between the 2 at same speeds same situations. Yesterday we drove CC (3:73 gears) and then a 4x4 with 3:73. There were some variations but the dually was still higher rpm wise, thus more fuel. The 2wd seemed more responsive than either the dually or 4x4, but they got me to buy the 4x4 since I was getting the truck below cost since it was on the lot for 90 days and costing them $ to keep. Wife liked it, I liked the dually (didn't need either one, wanted a 2wd truck SC) but you know how it is to keep the other 1/2 happy. I think there might be a slight difference between standard cab and any other due to the weight off set of the 4x4 or dually which are much higher weight trucks. As I said the 2wd CC was very responsive to throttle and felt a little lighter. Remember these were all back to back evaluations over about a 20 mile course of city and highway. The 2wd didn't have a computer overhead but the others did and the 3:73 gearing was showing about 15.5-16 on brand new trucks so I will have to actually find out what it will get when I get it home. Boy am I looking forward to that, but they put the spray in liner tomorrow or tuesday. Trip this comming weekend, gotta get the breakin miles going.

hank

 

These trucks are extreamly sensative to MPH and MPG.
This is one of the things that is frustrating people are running them at 75/85 and complaining................65/70 is a huge difference

 

The highway mileage doesn't bother much because I know that is basically, my bad, so to speak at low altitude cruising speeds I like to fly at.. Plus I haven't had the opportunity to get a good read for Hywy mileage yet. Leaving Friday for 1,600 + mile round trip. Will learn a lot then. Pump tp pump will tell a true story.

The city MPG is really throwing me off which is mainly why I asked those questions. Reported result on FTE is all over the plade on '04 & '03. Kinda trying to see a relationship to vehicle type but that is proving a monstrous task.

Pre Predator I was only getting 12.5 city. Just doen't seem right. Just loaded Predator Sat. A.M...It is unreasonable to try to caluclate new city mileage this week...Ha Ha Ha...to busy playing and watching for local L. E.

Predator FYI: Daddy likes it...Daddy likes it a LOT!

 

These trucks are extreamly sensative to MPH and MPG.
This is one of the things that is frustrating people are running them at 75/85 and complaining................65/70 is a huge difference

I really don't see how 65-70mph is a HUGE difference?? 65-85mph really is a huge difference. These trucks as we all know are big and aren't the most streamline in the world......so trying to shove them down the road @85mph is obviously gonna effenct the mpg negatively. I am not complaining about the mpg @85 mph. The mpg is actually pretty good in my opinion, but still wish I had the original flash so it would do a little better.....not to mention having the piolot injection back.

 

Just under 2000 rpm seems to be the optimum for the best mileage - that would be between 65 and 70 mph with 373 gears and there is a significant difference (decrease) if you run mine 80 or more. I am jealous at what some of you report for mileage but hope to cure that with an 05.

 

Run your own test you will find out, as Kurt has pointed out has to do with RPM

 

Under 2000 RPM...No can do with that new Predator I just put in.

Can't wait for the newness to wear off so I can see if I really do get a mileage gain out of it.

Of course, if it doesn't stop raining around here I'll stay under 2000 RPM by default. Dang it.

 

That's what 4x4 is for - a perfect match for the predator

Course that stopping thing still comes into play...
and that turning thingy too !


But at least by now all that oil has bee washed off the road...
along with some of the roads !

This morning in Mansfield, Tx they had to close 287 just because of the 4 foot of water across it

 

It is pretty easy to calculate the difference in RPM for a given speed for a 3.73 rear end versus a 4.10. Multiply the RPM for the 3.73 rear end by 1.099 (which is 4.10/3.73).

For 5-speed auto and 3.73 rear end with the stock tires which have a rolling circumference of about 30.5 inches at 70 MPH you'd be turning about 2014.3 RPM. For the same truck with the 4.10 you'd be turning about 2214.1 RPM.

A difference of 199.8 RPM. Double the speed to 140 MPH and the difference grows to 399.6 RPM, drop the speed to 35 MPH and the difference drops to 99.9 RPM.

This of course is in high gear, in the lower gears the numbers will be different but the ratio multiplier of 1.099 above is still valid.

Getting in a truck with the 3.73 and then into one with the 4.10 and trying to compare the tach differences for the same indicated speed isn't too accurate, nor is the overhead "lie-o-meter"

Daryl

 

I just finished a 295.1 mile loop from Carlsbad to Big Bear and back. I had the dirt bike in the back and was doing around 75 - 80 MPH on the highway and something less than 55 MPH once I got on to the secondary highways (Rt 330 and Rt 18).

I had the Superchips Microtuner Economy tune loaded and used 18.05 gallons for a hand calculated (well, I used Excel actually but you know what I meant) gas mileage of 16.35 MPG.

The "Lie-O-Meter" on the overhead claimed 17.2 MPG. I should note that my GPS shows that I was doing 77.5 MPH when the speedo indicated 80 MPH so my actual miles traveled were probably more like 304.6 and the actual mileage more like 16.8 MPG.

This wasn't all that bad considering that I was climbing some pretty good hills up to Big Bear and then was held up going down by slower traffic and couldn't coast as well as I normally would have.

On straight highway driving I usually see numbers in the 17 to 19 MPG range unloaded and with the Stock factory tune.

As I accumulate more data on the Econo tune I'll continue to post - probably in the SC thread.

Daryl

 

Cool...Thanks for the info. My trip will have it all in regards to terrain. Flats, hills & mountains. Once I get where I'm goin' she probably won't move til I come back. Pure highway with all but about 150 miles (2-lane) of 1600 miles.

 

Daryl your figures will compute pretty close just by the eyeball method. I dont like the tach as it is not set up worth a didly the way it is, but it will get ya ball park. As to the overhead I know its not accurate for what I was doing but it will give some indication since I reset it prior to driving off the lot. My f250 has 4:10 gearing and will pull the crap out of anything, just doesn't get any milage in use thus the move to the new truck.

But if ya figure with a 3:73 that 2100 will get ya 70 and at 2200 in a 4:10 you are only doing 65+- than you can get an idea that one is going to need more fuel to get to the speeds you think you will use. That was my whole intent, see what it took to go what I normally drive at.