smokin24v

wonderin what kinda RPM's give ya the best fuel milage i have a bad habit of shift way to early although id dosn't lug it i can tell cuz my EGT's will shoot up and i won't be goin but a couple miles faster than i did in like 4th..... and also what do u do differant when towing? thnx (pry sounds like a completely dumb ?)

hamilton71801

1800 is my sweet spot which puts me right @ 70mph. When towing I go by my EGT and boost gauge. Too many factors there...terrain, etc. but on flat ground 1800 is still my sweet spot.

Dartmouth 12V

The sweet spot for rpms is a function of the load. At WOT, the most efficient point is pretty close to torque peak and at no load, idle is the most efficient. All other loading conditions fall somewhere in between. I would recommend leaning towards more rpm than less rpm. If I am running empty around town, I run around 1600rpms and if I am on the highway, I make sure to be above 1700.

If you have a consistent route, try a few tanks with different rpms and see for yourself.

seahawkdodge

All I know, is that 2100 rpm is about 75 in my 98. Above that number on the highway, my mileage drops exponentially. I seem to get 20-21mpg highway, as long as I keep it at 70 or below on the highway.

1800-2100 is the normal "sweet spot" for cruising mpg.

GFB

More so because of increased drag, not increased RPM.

seahawkdodge

What ever do you mean? My truck is sleek

high bid

so by cruising to work like grandma' on the hwy @ 1500rpms (63mph) I'm making things worse in the mpg factor? I know you can't go by the overhead monitor completely but at 1500rpms (hwy) it shows my mpgs about 21.5.
I'm also rolling 315s w/a 4" lift

seahawkdodge

Not necessarily. As was mentioned by someone else earlier, a lot of it depends on load. With a light load, 1500 is fine. The only issue you might have with 1500 rpm, is with the 5th gear nut on a NV4500.

Drag increases exponentially with speed, so you are probably better off cruising at 63, than at 75...

WestTN

I run 55 mph and accelerate gently. Truck is all stock except for running the fuel saver Smarty tune. The last four tank averages were all between 24.1 and 24.7 mpg. The tires are also stock size 265's running at 65 psi.

cody_d

what kind of gearing do you all have, getting 20+mpg at 70 and 75mph? I have 4:10 with 285/75R16 and only get to the 20's when i'm around 50mph.

also, does anyone know if there is an internet calculator that i can put the axel ratio in and my tire size in and ''recalculate'' my ''new'' ratio?

Fishin2Deep4U

I get 24+ unloaded at 67 or so MPH. Slow down or speed up and it hurts my economy.

Towing for me is pretty light. Just a jetsled. And the same speed nets the best results.

I keep the Juice on 1x1 and use the cruise as much as possible.

3.54 gear/ 285 tire

Dave

Fishin2Deep4U

You ratio is still the same. If you are inquiring to effective ratio, that's a simple matter of using some percentages.

If we assume that you had 245/75-16, that is a tire height of approx. 30.50"

If you changed to a 285/75-16, that is approx. 32.8"

The difference would be near 7%. You can apply that to your gear ratio to get a new effective ratio of approx. 3.81 final gearing. You would need to go to a 4.387 gear to restore the previous gearing.

Keep in mind that your speedo reads 7% slow and you are traveling 7% further than your odo says. So, if you are getting 20MPG add 7%. That is about 21.4 MPG.

And at 60MPH indicated you are traveling 64.2 MPH.

Dave

Fishin2Deep4U

I get 24+ unloaded at 67 or so MPH. Slow down or speed up and it hurts my economy.

Towing for me is pretty light. Just a jetsled. And the same speed nets the best results.

I keep the Juice on 1x1 and use the cruise as much as possible.

3.54 gear/ 285 tire

Dave

seahawkdodge

I'm running 305/70/16 tires, and 3.55 axle ratios

klx650a2

My sweet spot is 67 mph also, towing or empty, best fuel economy... unless I'm towing really heavy (over 10k) then 60 works well...