Improve fuel efficiency in my M1009

[WARWAG]

A Banks Turbo will see you with better MPGs (If you drive it like a man and not a child).
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How old are the fluids in your drivetrain?
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When were your wheel bearings inspected and regreased?
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Are your POS stock WARN hubs stuck in the egaged position yet they say free? (My D60 had one bad warn hub that was always engaged diffrent axle but relates)
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How are your injectors? Injector pump? ect ect.
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These trucks and there related components are 25 plus years old. S.H.I.T. happens especially when someone drives them who doesnt own them.
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I did'nt buy my M0128 for its Fuel Economy. I bought it to see Tree Huggers cry everytime I drive buy them. If ONLY my truck could run off of Hippie Tears. That would make a great renewable source of fuel.

 

[scottladdy]

I did'nt buy my M0128 for its Fuel Economy. I bought it to see Tree Huggers cry everytime I drive buy them. If ONLY my truck could run off of Hippie Tears. That would make a great renewable source of fuel.

 

[still standing still cyco]

The research I've done shows people reporting slight increases in power and fuel economy by switching to a 3" single exhaust (are M1009s single or dual exhaust from the factory?). I plan on doing this soon for my M1010. The oem 2 1/2" Y-pipe from a smallblock gasser bolts up to the 6.2 manifold, and then run 3" all the way back. It's also supposed to sound great! I'll post the results after I convert mine over.

 

[scottladdy]

M1009's are dual exhaust from the factory.

 

[M1009 NEWBEE 2013]

When I first got my M1009 I was getting 20-21 on the 900 mile trip back home after purchase and then it dropped way off over the next 6-8 months to 15-16 but after a complete fluid, lift pump, new belts and GP change she climbed back up to the 20's. I am averaging about 18-22 consistently. Im sure it changes based on actual mileage, IP pump and other things as well. Mine has 63K original miles and Id like to think that may also be a factor.

 

[WARWAG]

Dont forget to check your tire air pressure. The higher the air pressure the lower the rolling resistance. That also makes a huge difference. Go with factory maximum PSI if the road conditions allow.

(This is just for the greatest MPG) I run my BFG BAJA 37s at 30 psi rear and 35 front Empty. Max load rating pressure is 50 psi. Im not worried about MPGs.

 

[Wagner]

How can you tell if the hubs are not working as they should.....not freewheeling, etc?

 

[chainsaw]

I don't know how to check for stuck hub locks, but I aim to find out. After having the IP replaced, injectors replaced, new air, glows, and fuel filter, topped out tire pressure (stock 31s), I have managed to improve my mileage from 11.5 to an award-winning 13.3mpg. I'm still searching for the silver bullet because there has to be one when I see some getting 14s and others getting 20 + mpg. What about replacing the FUEL FILTER PRESSURE SWITCH, the CDR VALVE, or VACUUM PUMP?? I've also figured out how to install dual ram air into the filter box and will be doing that shortly. Any advice on checking the hub locks out there?? BTW, if I ever get this MPG mystery solved, I will be sure to let you know LOUDLY!

 

[nyoffroad]

Stuck hub? Not a problem! With the hub "unlocked" jack up the front and turn the wheel while looking at that wheels u-joint, the u-joint should NOT turn. If it does turn slip a scewdriver in there and turn the wheel again ( it may be turning cause of old or cold grease). I've never had on sieze and stay locked, but weird things happen.
Fuel MPG? Everything on that truck effects mpg in one way or another. The only way the fuel switch and vac. pump effects your mpg is by there weight. So nothing gained there. I see your in MI. you do know that "winter fuel" has less BTU's and that means less energy per gallon and that means you have to step on the go pedal a little harder and that of course means LESS MPG! Add in the cold ATF and wheelbearings ect, and the slush and that takes it's toll also.
I drive a truck and see just about 1 whole mpg differance between winter and summer, that add's up to about $5000 a year! Best way I know of for the biggest increase is a 700R4 swap, I've got one in mine and will NEVER go back!

 

[nyoffroad]

BTW An averge number is just that ONE NUMBER, It cannot be 18-20 or "about" or "aprox." The only true way to figure MPG is from tankful to tankful even just a couple tanks can be misleading. If you 'top off' all the way vs. as soon as it clicks off auto you leave it, that could be a gallon. Do that on one tank and you could be happy or sad it's best to keep a book of fuel and miles over time you'll see a trend and know the REAL numbers.
And no I don't do this for my 1010 but I do for my big truck, thats the one that goes thru 100 gallons a night!

 

[chainsaw]

Thanks, nyoffroad. I'm going out to check my hub locks right now. I do suspect hubs because as I was doing a tight turn recently, I felt that familiar clunking resistance from the front end you normally get in 4X4 mode, but I was in 2X4. I did use 4X4 during a few of these crazy snowstorms, but I know I unlocked the hubs. We shall see.

 

[Soaper]

for the guy asking about why two batteries.
its an diesel. account for higher compression and glowplugs. youd kill an single battery out quickly.

it doesnt have 2 batteries just cause of 24V. IIRC just the starter side is 24V.

granted in summer you can get away with one battery. but in winter. your sol.

 

[m1garand_man]

I have done a lot of work to my 1009 to include dropping in a new engine 10k miles ago. I have never gotten better than 18 or maybe 19 miles on long high way trips at 60mph. I drive 40 miles a day on this truck now mostly 60mph and only get 17mpg. I maintain the heck out of this thing and it leaks literally no fluids unless its below 0 and then it will some times leave a dime size drop of motor oil from either the rear main or the rear of the oil pan. My injector pump and injectors were rebuilt recently but even when they were old and the injector pump was a bit leaky in cold weather I still only got a max of 17mpg. I will say that in sub zero temps my fuel economy can drop down to about 13.5-14mpg but that is not surprising considering the block is made up of over 700 pounds of cast iron. The complete engine is over 850 pounds. Putting cardboard over the grill helps a little with it warming up faster but not much.

Also for what its worth dirty vs clean air filter doesnt seem to make a noticeable difference in my truck nor did it with the old engine also I upgraded my fuel filter with a stanadyne FM 100 system with 5 micron filter. It didnt affect my fuel economy either way either but the truck doesn't leak fuel anymore. I will say that the water seperator bowl on the bottom of the fuel filter looks high speed though.

 

[al2ndWolfhounds]

My M1031 averages 11.1 mpg with most of my driving on country roads with some on the interstate. I have only pulled my trailer an 18 mile round trip so did not track the mileage. This week I replaced my rims and tires from LT235/85R-16E Steel Belted Radials to LT265/75R 16E1 BFG All Terrain on 16x8-6.5 OB Unique 297-7780 rims. I had 2 bad rims and two less than desirable tires. I am keeping the best of the old tires as a spare for my trailer under my truck and the new spare for the truck inside the center maintenance box. The new tire and rim would not fit up underneath the truck so that is why the trailer spare will be kept there. I will track and report mpg change if any with the tire change. Primary motive of changing tires was to get better traction off road and in snow.

 

[Barrman]

An easier way to check the front hubs is this:

Crawl under the truck and turn the front drive shaft while looking at the front axle hub u-joints. They will both start to spin and then only one will spin as you keep turning. If you can't turn the shaft with the t-case in 2hi, then you have locked hubs, broken t-case shifter or locked up front differential.

Now lock one of the front hubs. Crawl back under and spin the drive shaft again. The u-joint on the other side of the truck from the locked hub should spin. Unlock the first hub and then lock the other side. Crawl back under and spin the shaft again. Now the other unlocked u-joint should be spinning.

You can also just lay down in front of a tire, grab the u-joint at the axle end and turn it. Lock the hub in and it shouldn't spin. Repeat on the other side. I gave the longer version to try because it also test the t-case and differential.

Just a common problem thing to look for here is the front axle shaft u-joints. They could be 30 years old and rusted solid. That would give you the funny feeling while turning as they don't want to bend anymore.

How are the brakes? Another common problem with the CUCV style caliper is the pistons stick and cause lots of drag. The caliper mount pins could be more rust than grease as well which will also cause a brake drag. At $12.00 each, new calipers are pretty darn cheap and easy to fix. Throw on new hoses while you are in there.

Another list of things I haven't seen mentioned in this thread yet:

Ip timing. Are the lines lined up or at most the IP line no more than 1/32" to the drivers side of the block line?

195˚ thermostat that functions? A cold engine is never going to get good mpg.

Rear differential fluid full and the proper weight?

Same with the transfer case fluid.

Then the odometer and your fuel filling habits. Are you sure it is accurate? One of mine is 8% slow, another is 6% slow and a third is 2% off. That is compared to GPS and the interstate mile markers. Find out how close yours is to correct. The big filler neck in a CUCV can get another 2-4 gallons in the tank after most fuel pumps click off. I live 5 miles from the nearest fuel station and fill mine to the brim with lots of patience. Very consistant mpgs as a result.

Finally, there is the fuel itself. I used to get 20-22 mpg on my M1009 and 17-19 on my USAF surplus 6.2 powered Suburban. Now my fuel is federally mandated to have biodiesel in it. I have noticed a 10-15% drop in mpg in all my diesels as a result. What kind of fuel are you getting? I can add Powerservice or Stanadyne fuel treatment or my favorite, Ams-Oil treatment and get that 10-15% back. I have played with 2 stroke oil, but this cold winter has seen too many mornings of idle warm up time to see if it works or not.

My other M1009, RED, gets 17-17.9 mpg on every tank. It has more power than my original M1009 though which is now getting 18.5-19.8 mpg's. RED has more pep and climbs hills better though. They are all different somehow.

A last thing to consider is the gear ratio. 3.08:1 is what is supposed to be in there. However, civilian K5 trucks also had 3.42:1 axles. Are you sure yours in still 3.08:1?