Engine/Transmission (1998.5 - 2002) Most efficient RPM for economy

[RRuggles]

I have a 2001 quad cab 4x4 short box automatic with 3. 55 axle. While towing my 5th wheel at 55mph I average around 11-12 mpg in overdrive. I towed at 65-70 and my seat of the pants feeling is that I was getting about the same mileage, which makes me wonder if the higher rpm is at a more efficient power range. Haven't checked to see how it compares with theod off. Anybody have info on this? Thanks in advance.

 

[Turbo Horseman]

My understanding is that the most efficient power range for our trucks is 1800 to 2200 rpm.

 

[DirtyDodge]

I am not sure about loaded, but unloaded I get about the same milage at 70 mph as I do at 77 1/2 mph using cruise control according to the mpg gauge on the overhead console.

 

[VicR]

my results have been the same as Turbo Horseman. Once you get over 2200, the MPG's drop off pretty quick.

 

[rweis]

Most efficient rpm I think is zero, but you don't get too far too fast.



Little humor, very little.



Bob Weis

 

[Lordsman]

Boost

Keep your boost down, around 5psi or below to get top fuel mileage. There was a good article on this in the TDR magazine a while back.

 

[onestackdram]

my wifes 02 @ 1800 feels like a dog and doesnt SEEM to be getting very good mpg, but at 2000-2100 it feels much more responsive and SEEMS to get a little better mpg. Dont trust your overhead console they are not accurate. Her's is off almost 2. 5-3 mpg at any given point and will move between those two numbers for no apparent reason.



Russell

 

[pwr2tow]

See signature for in and out of O. D.



Best power is suppose to be between 2000 and 2200, although charts show up to 2600RPM's.



Calculated by hand.

 

[Hohn]

Your gauges will unlock the door the the highest mpg that YOUR truck is capable of. Remember, the mpg varies quite a bit from one truck to another.



It's not so much ENGINE rpm that determines mpg. Otherwise, you would get the same mpg at 2K rpm in 1st as you do in OD-- and we all know that's not true.



Now engine rpm DOES play a role in overall efficiency, since there are certain rpm ranges where the engine is most efficient.



Monitoring your pyro and your boost gauge will give you a good idea of how hard the engine is working. The lower you can keep these readings while on the hwy, the higher your mileage will be.



This is especially true of the pyro, since it shows you about how much fuel you are burning. Once the boost comes in, it's not so accurate-- but the trend is still observable and the rule of thumb still holds.



Generally, max fuel economy will come in the highest gear at the lowest load, and at the lowest rpm where you can still burn the fuel efficiently.



If you want to prove this to yourself, rent a dyno for a few hours. You will find that if you go about 50mph in OD with little or no load, then our trucks can approach the HIGH 20's for mpg-- 26, 27, even 28 mpg!!



The reality is that you will always have MUCH more load on the engine than under these circumstances, so mpg suffers. The amount of hp required to overcome aerodynamic drag increases DRASTICALLY once you get over 50 mph or so. Do the math and you will see that doubling speed requires FOUR times more power to overcome aero drag.



So the mpg tapers off in OD after a certain rpm (2200 some have reported) not so much because the engine is less efficient at that rpm, but INSTEAD it's because you are traveling faster and placing more load on the engine. Thus, it has to make more power and burn more fuel.



Justin

 

[Ncostello]

Actually 0 RPM might be least efficient of all since no measureable work is accomplished. Or rather... "undefined" since output/input = 0/0. Just a little more dry humor and fun.