I am a diesel man. However my powerstroke is about 10 years old and its soon to be replacement time. I am considering a V-10 instead of the 6.4. Which ever I get the truck will have the six speed and a gear vendors overdrive unit. I want your opinions on what is the most efficient rpm to set the truck up at 70 mph. This will be for the truck only as I will down shift when towing. I will make the ratio changes with the gear vendors, tire size, and finally the rear end ratio if necessary. Also, what mileage do you think is possible with the right set up? Thanks for your input.

 

Like the PSD, V10s are most fuel-efficient when kept under 2000 RPMs but I'm sure there is a point where engine "lugging" starts to reverse the savings. Unfortunately, I don't know what that lower limit is. Perhaps you can find out and let us know!

As for maximum attainable mileage, I don't know. Depends a lot on where you drive and the conditions that are uncontrollable such as weather, wind, traffic, etc. There are some MPG threads somewhere in this forum where you can see what various people have reported. With all the hardware you're willing to acquire, you might just set the record!

When towing, let the engine rev. Remember it's not a diesel and it won't blow up if you run it over 4,000 RPMs. It'll suck some fuel, but will turn that speed all day long and never complain.

Finally, not to try too much to sway your wish-list, but I highly recommend the 5-speed auto tranny and integrated "tow command" system. The new automatic is much, much, much better than the old E4OD (and derivatives). And having the tow system integrated makes it even better!

 

Read a post on this by another guy who suggested that @ 70-75 MPH you should be turning 2100-2250 RPM. It was in a thread on HP vs. torque and seemed reasonable.

 

Thanks for the input. I have been calculating transmission and rear end ratios to figure out rpms at different speeds. I guess I just need to do more research. I may have to just decide on a truck and do some real world testing before making the mods. Thanks for the opinions and keep the help and suggestions coming.

 

arrange your gear tire selection to yield a cruise @70~75MPH of 2100~2250 RPM and you will have about the best range for OD in modest hills and flat lands with or with out a good load....you can gear it a tad lower like 1900~2000 for the cruise RPM but in my experience in OD when you climb a mild hill she will want to shift out of OD hunt a little and then drop one gear.... the lower rpm usually works OK for empty running and gets about 1 MPG better but if your truck is gonna spend some time with a modest to heavy load you will like setting it up for the slightly higher RPM.... I have dicked with this for seven years now on all three versions of the motor and about all the "stock" tire diameters and gear rations.... I always shoot for the 2125RPM at 75MPH and seat of the pants it is the best for me with the CC kicked in and auto tranny...

The manual tranny, gear vendors and 4.10 or 4.30 options will give you a much wider range of options....

a lot really depends on what is more important to you....Max MPG is in the 1900~2000 zone.... best cruise comfort with least shifting is in the 2100~2200 range IMO

Look at my sig and understand I have owned 13 of these trucks with the V10 now... mostly 350s but a few 250.... I tend to run stock and empty 80% of the time and when she is loaded it is mostly to the Max of 22K pounds.... I also live in Texas where 80 MPH is the legal limit on the long roads I run...I also do three trips a year over the tallest passes Colorado can throw at you.....In other words I think I have a clue about what you are asking

 

That is exactly what I get. 2100 rpm at 70 mph. 6 inch lift with 4.30 LS