What RPM do you guys Get the Best MPG's at?

[F18hornetM]

I get my best MPG with the engine shut off pulled out

Seroiusly, only checked it twice and got a little better than 9. Run mostly around 45, never over 50. Also never drive it hard. Never in a hurry using it.
Somebody mentioned it, but some of our new diesel trucks dont do as well as these old things do on mpg.

 

[gimpyrobb]

2000 rpm is wher your best numbers are at. HP and TQ are at the higher end of their range and fuel conumption is at the lower end.

 

[Odyssey M]

Forget about MPGs and tweaking fuel components. I am going this route:

 

[Wildchild467]

I wish I would have adjusted the valves when I had the radiator out valve covers off and did a flush and new hoses a few weeks back.
Quick Question: is it pretty obvious knowing when the valve is fully open (by turning the motor) before starting the valve lash adjustment?

adjusting the valves is not that hard to do. it shows how to do it in the TM. you only have to rotate the engine to two different places. it takes about an hour and a half to do maybe. i would definately check your valves especially if you never checked them. treat your multifuel engine good, and it will be good to you

 

[Katahdin]

I just finished a 300 mile highway trip to the Maine Rally and back. Google maps said 300 miles, the odometer read 288. Got a hair over 8mpg in my 109 using an unscientific mix of approximately 50% pump diesel and 50% everything else. I tried to keep the rpms at about 2250 which usually equates to just under 55mph on the flats. The front driveshaft was removed and the ten 9.00x20 tires were 60psi all the way around.

 

[m816]

I never checked the MPG on my deuces and now I only have five tons to worry about.If I was getting any thing over five in the five tons, I would be happy. Actually, I am happy just tooling around in anything green.

 

[lawdog1623]

i figure mines getting around 10 mpg at 2200 rpm consistently. Thats bout the best i think im gonna see. I bet my 109 wont even be in double digits running downhill

 

[LowTech]

It's little hard to figure w/ how we fuel but,
We seem to get around 8.5 in the She Beast running around 2,100 - 2,200rpm w/ 395's at 30psi in the rear and 40psi in the front . . . pulling a 105, and we do NOT live where it's flat. No pump fuel used.
(and I think I need to turn her fuel down, too much smoke)

 

[bajajoaquin]

Here some data for the LDS, the LDT should be close.

This is a really interesting graph.

I had always understood that the RPM of the torque peak was where the engine got its best fuel mileage. The idea is that the torque peak is the point where the engine breathing is most efficient. Maybe diesels are different because they're not throttled.

But that chart indicates that the torque peak is at about 1700-1800 RPM, but max fuel efficiency is just under 2000. Still well below the max hp speed, though.

Really, really interesting.

But back to speeds and tires: this says that if you have larger tires, there may be a point where you can get better mileage in 4th than 5th. Someone would have to do a speed/rpm curve with the different tires to find out if there's a point where you would have rpm below the efficiency point in 5th but you could raise it to the 2000 rpm mark in 4th.

 

[bill2444]

I usually pull down a solid 6 mpg. running usually around 2200-2500 rpm

 

[peashooter]

M35A2/M109A3

so far my 109 is getting about 8mpg with cruising @ 2K rpm (45mph). Tire pressure is 65psi front, 55 rear.

Just got back from a 100 mile round trip. This time I was running 2200 RPM and got 9 mpg. Since the other trips however that were giving me 8 mpg, I adjusted the valve lash per someones recommendation. So I cant be sure if the higher RPM, Valve adjustment or both were the reason for the slight increase. Next trip I may try 2k rpm again and see if I go back to 8mpg.

Also I scratched a line in the fuel tank fill sleeve so I always fuel it up to the same point to figure out the mileage.

 

[Z71]

My non turbo M109 does not do too good - usually around 6 MPG at 55-58 MPH. What is the recommended valve adjustment interval on these multifuel engines?
I never adjusted mine to date, I assume they are screw and nut adjusters.

 

[Z71]

I usually pull down a solid 6 mpg. running usually around 2200-2500 rpm

Thank you for a very realistic MPG number. Mine gets about the same. Anybody gets 20 MPG?

 

[peashooter]

My non turbo M109 does not do too good - usually around 6 MPG at 55-58 MPH. What is the recommended valve adjustment interval on these multifuel engines?
I never adjusted mine to date, I assume they are screw and nut adjusters.

The TM says .025 for exhaust and .010 for intake. The TM is 9-2320-361-34 page 3-26. Some people go .015 for intake.