Increase mileage

[Dunedain15]

Piggybacking off this thread, diesel's at $4.39 in my area right now. Even with my $0.08 off with my Sheetz card, it still took $162 to fill my Suburban last fillup. This is getting old. I usually get about 13.5-15 (don't do a lot of highway driving). The past 2 fillups have been 13 and 12.5, though. I'm chalking that up to how much 4WD I was doing in the snow and ice.

Here's where you guys come in. What's the best way to increase mileage at this point? Everything I've done to it so far is in my signature. The next step would be to change the gears from 4.10 to 3.42 or to get a Heath tune. I used 4WD a bunch this winter, so I'm leaning away from the gears at this point for fear of what I'm gonna get myself into on the front. I'm skeptical of the gains I'll get from a tune, though. Seems like the physics behind the 4.10 ratio will always yield the same results. I'm happy to be proven wrong though. I'm not really interested in power; I'm after MPG. I love my 6.5, but I might have to think about going to gas/propane if things don't improve. I look forward to hearing your thoughts. Thank you, Gentlemen.

 

[schiker]

What temperature thermostats are you using? 195F gets better mph than 180F.

ATT (turbo), tune, then drive slow <60mph.

 

[Dunedain15]

What temperature thermostats are you using? 195F gets better mph than 180F.

I don't know. I hadn't touched the thermostats since I bought it, but I had it at the shop recently for an issue with my heat. They said one of the thermostats was stuck and the other looked like it was for a Cummins. They replaced both. The receipt said ACDelco Premium, but they didn't list temps. However, I did notice my temp gauge now sits at 190 - 200. It used to sit at 180. I can't afford the ATT right now, but a tune for the stock turbo is within my grasp.

Thanks for the feedback.

 

[Will L.]

What are the high output injectors exactly? As in higher volume of fuel for more power and less economy? Do the bigger turbo before gearing changes, it will pay for itself. How many miles do you put on city vs hwy per month? Also external overdrives are available. I know a gear vendor type is only good for the rear axle drive, just make sure you disengage it before going into 4wd, you are not full time 4wd, right? btw incase anyone is full time 4wd and thinking of the conversion for economy, don't, I tried it and wish I had not. zero gain.
When not dealing with weather, do you have a set of taller skinny highway tires you could run?

 

[JayTheCPA]

Depends on how much you want to spend.

K47 airbox will probably get a small bump. I do not recall whether the 98 has the intake snorkel; if it does, remove it.

Tires. AT's will cost about 10% compared to HT. As I do not do any mudding, I use Load Rated E HT's and run them at 80 psi to squeeze a little extra mpg's out of them. On dry pavement, the Burb handles nearly like it is on rails. If I need to get through the snow or soft terrain, I drop the psi's accordingly.

If the comment to re-gear is truly serious, take a look at GearVendors as last I checked the GV conversion costs nearly the same as re-gearing a 4x4 (presuming you are paying for labor and not doing it yourself). To date I am only aware of one person whom had an issue with the GV.

 

[Dunedain15]

What are the high output injectors exactly? As in higher volume of fuel for more power and less economy?

Good question. I got a knock after an incident of heavy acceleration. I called Heath Diesel to confirm my suspicion of a bad injector. Bill recommended these Canadian made HO injectors. He said as long as I'm not pulling a lot of weight, I'd see better performance; with a lot of weight it would just make EGT's go up.

How many miles do you put on city vs hwy per month?

I'm gonna go with 80% city. Outside of that, it's country roads with lots of hills and turns.

you are not full time 4wd, right?

Nope. I live off an alley that doesn't get plowed. Also, my city isn't great with snow removal in general, so I use 4WD when needed. Since I'm around 80% in the city, I needed it a substantial amount of the time this winter.

When not dealing with weather, do you have a set of taller skinny highway tires you could run?

No, but that's something I've considered. Another set of rims and tires is gonna be pretty steep, though.

Thanks for the feedback, Will.

I am leaning toward the Heath fuel economy tune because it's in my expense range (~$500). I've talked to him before about it. He said he's got one for power and one for economy. I know most guys here are after power, but does anybody have any experience with the economy tune from Bill? Thanks.

 

[Dunedain15]

Depends on how much you want to spend.
K47 airbox will probably get a small bump. I do not recall whether the 98 has the intake snorkel; if it does, remove it.

It had a cold air intake on it when I bought it. It's not a full box, but it has an L-shaped separator that keeps the filter away from the engine heat.

Thanks for the info about tires. I'll check into that as well.

 

[JayTheCPA]

I know most guys here are after power, but does anybody have any experience with the economy tune from Bill?

The Burb's current tune is Bill's (as of last Summer) and last I talked with him, the tuning was to the customer's usage and there really were no standardized 'economy' or 'power' tunes as he burned each one after talking it over.

Back to that air box . . . If you are getting a fair amount of drone, might want to consider tracking down a K47. When I got the Burb it had an aftermarket 'L' box and for grins I installed a K47. What surprised me was that the K47 (and custom plumbing) noticeably dropped the drone.

 

[RI Chevy Silveradoman]

I think you may be chasing after something that is completely unattainable. The burb is very heavy to begin with, coupled with the 6.5 engine is not a high mileage capable set up. And the city driving gives you the worst mileage possible. With winter fuel, your already at a disadvantage during cold weather. It is like someone dangling a carrot from the end of a pole, and you can never reach what you're looking for.

Maybe get a Fiat 500 or Smart car? Or a diesel Jetta TDI or something along those lines.

 

[Drago]

Im running homemade BioD thru my two trucks @ about 1.50 a gallon not counting sweat blood and tears, let us know if you want to sell

 

[Paveltolz]

I ran a version of Bill's Economy tune with the old motor and GM-5 w/ TM. I saw a slight increase in MPGs but, to be fair, I got better with an ATT and a more playful tune (also by Heath).

 

[tanman_2006]

Between exhaust and an MPG tune I only saw 1 mpg bump on Highway average but I stopped getting a random 20mpg or more tank.

In town I found a vin f tune and light foot helped the most as well as 100rpm lower idle.

I have a custom multi tune currently available from leroydiesel.

Source Unknown

 

[Dunedain15]

I think you may be chasing after something that is completely unattainable. The burb is very heavy to begin with, coupled with the 6.5 engine is not a high mileage capable set up. And the city driving gives you the worst mileage possible. With winter fuel, your already at a disadvantage during cold weather. It is like someone dangling a carrot from the end of a pole, and you can never reach what you're looking for.

Maybe get a Fiat 500 or Smart car? Or a diesel Jetta TDI or something along those lines.

I get that feeling every so often. My daily driver is a 2002 Chevy Cavalier. The Burb is the family bus. Unfortunately, my four kids, my wife and I won't all fit in a Fiat 500. That'd be something to see, though.

 

[Dunedain15]

Between exhaust and an MPG tune I only saw 1 mpg bump on Highway average but I stopped getting a random 20mpg or more tank.

In town I found a vin f tune and light foot helped the most as well as 100rpm lower idle.

I have a custom multi tune currently available from leroydiesel.

Source Unknown

I didn't know Leroy did tunes. Leroy, you do tunes?

 

[tanman_2006]

He sells them for a reputable tuner that goes by Kojo.

 

[Burning oil]

I can get the KOJO or an ATT (for GMx) tunes $350 and $310 respectively for OBDI. KOJO OBDII I think was same price I'd have to confirm first.

The ATT turbo with will get most pepole atleast 3MPG ^. Tstats, tune and turbo are the main componients to better MPGs, but it never ends. Im after a MPG build myself. Im kind of stalled waiting for parts and now Im leaving for two weeks. Anyway I hope to get 24MPG hwy when done.
A bonus is power adders usually get you better MPGs as long as you drive with a light foot.

 

[Chevypoor]

The best mileage I have seen out of my fleet was 22.6. That was Gary, a NA motor. Gary usually gets 19.8-20.5. Little D was getting with 18-18.5 with a Heath tune and Turbomaster. Larry with the ATT and a Heath tune seems to be getting 18-18.5. In both Larry and Little Ds case a Trac Rac seems to cost around .5 mpg. In both trucks the mix is 40% or so city and the rest is highway. I also try to keep my max speed at 70. In my case the ATT seems to have netted me about 1-1.5 more mpg. I average 40-50k so that mileage increase is substantial.

Go with highway tread tires, keep the tires inflated at max psi, and increase engine efficiency/ breathing not only pays off in higher mpg but less wear and tear. If we could stand driving at 65 max preferably 60 and we would all be shocked at the increase I think.

 

[ak diesel driver]

my mileage really starts to drop above 60 but my rack probably is worse than the trac racks

 

[GM Guy]

I havent went on a "empty" run with my 95 GMC, but with the service body on, 100 gallons of diesel in the bulk tank, and a/c on, it got 20.xx mpg. after ditching the service body and putting the gooseneck hitch on, pulling the trailer it gets as high as mid 15s empty (10-11,000 lbs), and 10-13 loaded (15-20K lbs).

my 99 chassis cab at 8500 lbs empty (service body with some supplies) has gotten 18.5 MPG. both of these are 4.10 gears.

the 96 GMC with 3.73s has gotten an all time fleet best of 23.xx mpg. my 91 GMC with no OD and a EGR system has only gotten as high as 22 mpg.

as far as my low dollar recipe for MPG, it is
wimpy highway rubber, or all terrains, usually 245/75R16s on the SRWs. I like getting them off craigslist or the like allready mounted on the nice light weight PY0 alloys.
air dam off a 1500 (2wds dont have tow hooks, so I like finding a K1500 in a junk yard, and getting the hooks with all bolts and brackets, and the airdam with all the hardware)
functioning vaccum operated wastegate system. The factory turbo is restrictive, and the OEM control will open it up when cruising for less restriction.
195 degree AC delco stats.
driving slow. 2250 RPM is about all I do when i am trying to get MPG. 1900 is what gets the best.
K47 air cleaners. I imagine it helps MPGs, but the main reason I do it is the better filtration over the 92-96 flat panel.
I doubt it helps, but I run Fluidamprs on as many as I can.
stock output injectors. I feel that unless you are shooting for the 300 HP number, you dont need HO/ marine injectors.

sadly I havent even fully serviced many of the diffs (just make sure they are full), but I need to get some amsoil in the diffs.
after recovering from paying tags and insurance, I need to get some Diamond Eye 4 inch exhausts.



if someone gave me some $ to dump in the fleet, the first thing I would do is go with:

an ATT. I would try stock computer for a while, but may get a tune.
3.42 gears. may actually hurt MPG in town though.
full synthetic, tip to tail. not that expensive, but leaks are expensive, so that means some seals and gaskets and labor to take care of that.


as far as advice, do what you can for aerodynamics and rolling resistance, and driving style. try some hypermiling tips, like use the momentum to your advantage and try to time stoplights, let off, and roll up to, and hopefully through, rather than run up and club the brakes and stop.

good luck!

 

[hookedup50]

Empty and behaving (72mph) and old lady starts I get 19ish combined with heath tune that was for gm8 and TM. I have the ATT now and will send out the ecm for reflash when I am working again(back surury this week). My goal is 21 22+ and may not be realistic without stuffing a 6l80e in the truck. I have to kill the 4l80e first and not trying to so that could be years. I think a burb is lots heavier than a pickup though so if Leroy is trying for 24 in his burb there is hope for me.