I have probly about 350,000 miles or more (odometer doesnt always work) but she still runs excellent. Im getting about 17 mpg average with some smoke in the power band. It has 4.10 gears with 5speed and 31 inch tires 235/75r17 I think. HX35 turbo silencer MIA with stock intake going to the stock airbox but it has a k&n cone filter with a pvc adapter that I made and the box is closed. exhaust is a 3inch down pipe to 4inch to 6 inch stack. Pump mods 3200 gov spring, stock fuel pin, idle cranked up for winter 800 rpm id say, starwheel turned a bit, full throtle screw backed out, power screw untouched I beleive. What should I change to get the best posible tune for best MPG I think my big limiter will be my gears but I dont have money too change them so we will have to work with what I have. I would like to aim for 20 mpg or better

 

If it's a dually 17mpg is about what you will get. An auto will get worse mileage than a stick. Stock sticks at that many miles will be dirty and worn causing less mileage. My auto trans dually with stock sticks, and 297,000 has gotten 17mpg since about 1996. I've read that's about what other similar trucks get to. A manual srw with good injectors should get 20+ with a reasonable driver.

 

Im pretty sure it has aftermarket injectors because if I pull the stock pin out and stick my denny t in and tune the pump for racing it will dump coal and it rapes common rails and duramaxes. What if I bumped the IP 1/4 it is still at the stock mark?

 

in the magazine i read they swapped the stock 4speed for a 47RH OD trans and got about 24mpg highway from the stock 4speeds 17-19 they were getting. but you said money was a factor here and thats probably not the cheapest route to go, just an option. also methanol injection should boost you up 2-3mpg if you can cough out the cash for a set up. another route to go is boiling up some biodiesel, wont raise your mpg much at all if not even drop your mpg slightly but you could cut the cost of fuel in half doing this. just a few options!

 

I hate autos so I have a 5 speed. My brother had a couple g56 6 speeds a while back so that could have been a option but the clutch was over a grand at southbend. Im pretty sure if I fidle with the pump a bit more and try to get rid of the smoke and bump the timing 1/4 inch it will improve.also bio diesel may be a short term option since my my mom has a mercedes with VO system and she has 200 gallons of VO but a BIo diesel system takes alot of space and is fairly expensive as well. Would a BHAF do better then a k&N? I also have a 2nd gen intake horn just laying around will that do anything? will my intercooler hose work? What about synthetic lubercants? Im pretty sure I can do better than 17mpg with the ammount of smoke I get. I wonder what it would take to make my own water meth injection system

 

actually to make your own meth kit its pretty cheap! just gotta get the right pump and right injectors then the rest is just a small tank (windshield wiper fluid res) and some cheap hoses you can buy at the local auto parts store, also the programmer for it. check up on snows website for the stuff get some prices and as for the VO stuff you dont really have to have any sort of "system" for it, just clean out the veggy greese and pour it in your tank depending on the weather 50/50 is good (also mixing the veggy oil with grain alcohol increases the combustibility rating of it) ive actually seen people JUST run 90% veg oil in their regular fuel tank, i personally do not recommend this...and also you have to make sure this stuff is CLEAN straining it through a couple of towels will not suffice its a long process but well worth it if you get a system going. and a 6 speed would be really nice i dont like autos either but like i said the magazine i read they used the auto trans and upgraded to the OD trans and made 550ish hp on it and got like 26mpg in the end! so this is what im bassing my build on..i dont plan on 550 hp but i do plan on a powerful reliable beast with some good mpg numbers

 

Well we can talk about transmissions all day long but some basic things you can do are:

tighten the star wheel in the AFC. This will cut back on wasted pre boost fuel without affecting over all power. Basically your foot and your MPG will be more in line with each other.

You can back off your power screw. If you get anything darker than black smoke at full throttle this needs to be done. If not, being conservative with your foot would be enough.

Advance your timing (if you haven't already)

Keep a clean air filter and fuel filter on the beast.

These few things can make a huge difference

 

Your turn the star wheel left to tighten it correct ? And right for more smoke and pre boost

 

Correct. You want it to move up the threads, counter clock wise

 

In your opinion would a bhaf do better then my intake setup

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what do you think the best way to figure out your MPG. With out runnig a full tank of fuel. since it takes 8 to 10 days to get through a tank for me