Help with my MPG before i throw in the towel

My 96 FLD midroof with a 11.1 detroit got a steady 7.4 unless I ran over 68 MPH or so.... my 379 does 5.6 to 6.3... yours should be a lot better.

The tires size won't make any difference you'll notice... the turbo wing is useless (sorry)... don't expect any mileage improvement with the FASS system, either (although they do have some benefits).

Air up your tires, make sure you have synthetic lubes in the boxes and rears, use progressive shifting and the cruise whenever practical, sloooow down and don't check your mileage after every fill (a bad headwind will hurt your short term numbers). Check you fuel economy over at least 5 tanks of fuel to give you a accurate reading.

Also have your fuel mileage checked on your ECM... you may be surprised that your mileage is better than you thought.

 

for what its worth i did a upgraded turbo (non wastegated) a straight thru muffler and a tune from erich and ever prior to the tune i was up .5 mpg. turbo was super lazy without the tune tho really sucked to drive
a few more details
http://www.thetruckersreport.com/tr...ighteen-wheelers/138268-new-ecm-thoughts.html

 

Fuel quality has been a concern recently... at least heer in WI amd the UP of MI.

I have a Mobil truck stop here in my hometown and i like to buy my fuel from him... but lately I'm getting .75 MPG less with his fuel than the fuel I buy at two other mom and pop places that I frequent.

I called my engine guy and he told me he has been trying to get MI and WI to respond to his requests about testing the fuels used in his area since the local loggers have been screaming about piss poor mileage this winter.

 

as stated above by rambler... IMO too, if your turning 1600 at 65 mph, your gears are working against you, truck spec'd poorly when built or not what u need. Optimal fuel milage usually means shifting around 1400 rpm, and if your driving 70 mph turning 1700 or so your mileage isn't going to improve. Slow down, shift earlier, drive w/ your ears (turbo) if you hear that good ole whistling sound a lot then your pouring that $$$ out the stacks. Once u get moving and up to speed, wind resistance is the #1 cause of poor fuel mileage, not rolling resistance (weight)

 

here is a key thing to watch when dealing with fuel mpg ur turbo boost gauge if u have one u want to keep that thing under 10 psi on level roads in order to get good mpg if its not staying under 10 psi ur pissing the fuel away. anther thing to do is to get the truck up to speed(say 65) again on level terrain let go of the gas pedal and see how fast it slows down .if it slows down feel fast u have resistant issues.

 

If you drive this truck at 60 MPH n do yer best to not get over 10 lbs of boost will help alot. Tires should be lo-pro's like Bridgestone M720 or M710 or Michelin XDA Energy all for low rolling resistance. Get an oil sample from your engine and have Detroit do it, not speedco or some other shop. Have yer charge air cooler checked and inflate all yer tires to 5 psi over max. You will see a BIG improvement right away even before replacing tires...then it will get even better. I have a '98FLD120 condo pullin a vans with a 3406E 13spd n 3.73 rears on LP24.5's. I drive it at 60 mph n get well over 7 mpg average

 

Like the last 2 posts I agree, the easiest and cheapest way to improve mpg is watch your boost gauge. If you don't have one a $25 0-50 psi pressure gauge and some tubing and fittings and now you have one.

I have CAT but I try to keep below 5 psi on the level, under 10 on slight grades and don't "get a run" at a hill, just hit it at your normal speed and then drop out of overdrive and you should be able to pull in direct at around 50 mph. That is a good speed because you are not wasting much fuel trying to push air. All your fuel is being used for truck friction and fighting gravity. No need to add air resistance to the mix.

The wing should get you a solid .25 mpg. I had one when pulling vans so I know. You need to have it set right though. I see too many guys with the wing mounted way too far forward so the air just drop back into the gap before it gets to the trailer .
If you run a straight line up from behind your sleeper wall, your wing should extend a few inches rear of that line. Mine might have been about 4" IIRC. You want it close as possible to the trailer without it hitting when you turn up a steep driveway.

And try 50 - 55 mph, let gravity run you out as fast as you feel comfy with on the downhills and leave the cruise off because cruise is designed to keep a certain speed, not to conserve fuel.

Running coast to coast it will suck running that slow; you either run slow or pay the price to run fast.

Also check the weather for wind speed and direction. A lot of times the wind usually dies down at night so you can save $$ if you are running into the wind by laying low in the day when the heat creates more air movement and then running after dusk in less wind. Or if you have a tailwind use it to your advantage. Example - my last run to TX wind was 21 mph from the NW and they forecast only 7 mph that evening. I got loaded and went back home until the sun went down and then hit the road.

I have been known to get over 8 mpg DH-ing with my mechanical CAT and flatbed by driving between 50-60 mph. The 62 mph governed, cruise-control-one-speed sidewalk sissies get flustered because I drag 'n fly on the rolling hills so we'll pass each other a few times until the terrain let's the cruise control driver get some ground on me. I guess they think I'm messing with them. They get ticked off and cut me short after passing me. Then I gotta jump in the left lane so I have some safe space in front of me, oh it turns into a whole stupid game with these cruise control zombies.

 

I see you are Fontana,CA, what are you pulling? Reefer,heavy loads? There's no easy way in and out of California ; heavy pulling long hills on I-5,8,10,40,15; and windy ; i wouldn't expect a miracle 8MPG ,even empty. My last truck was a Volvo770,2001/ with. Detroit D60 12.7L, i pulled 4 months reefer from CA, blew the motor; imop 12.7L Detroit is too underpowered for heavy loads in and out of CA.

 

keep your speed down will help the most drive like you are broke .