What's your fuel mileage with a load?

[jeffreydmet]

I bought a K3500 4x4 crew cab with AT about a year ago. I have been very disappointed with it. I bought it to save a little fuel over the same truck I had with a manual tranny and a 350 gas engine. On a recent trip to CO I averaged about 11mpg on open interstate pushing the speed limits. I got 10.5 on about the same trip last year. The best I've ever got unloaded under ideal conditions is 16.5 but 13.5 is typically what I get unloaded.

I generally pull a 4000lb hi-lo type camper and about 3000lb in the truck. I have checked such things as TDC (now -.88) and the torque converter clutch.
Does anyone else pull a similar load? What kind of mileage should I expect. So far this truck has been a waste of money over the gas. I think something must be wrong that I or the dealer are not finding. Any suggestions for modifications that would help?

[ktmracer]

i have a 2000 4x4 crew cab,3500,dually,auto w/ 4:10 gears.best unloaded= 14.66mpg@ 70mph running the a/c. this is with a 5th wheel type tailgate.w/ regular tailgate subtract about 2 mpg.i have a 39ft,high profile, 5th wheel, toy hauler ,that when loaded weighs approx.(guesstimate) 13,500lbs.withthis load,at 65mph or a little faster i get about 7 mpg. i too originally thought my mileage should be higher. but after doing a lot of homework and talking to a lot of people i find this is in line w/ the new generation d-max,p-stroke, but not quite as good as a cummins. a single rear wheel trk or a 3/4 ton should get better mileage. i`m happy w/ mine.a big block gasser pulling about the same load as me was getting 3-4 mpg.

[Johnny B.]

My 93 dually gets about 13-14 unloaded with the A/C on in town or on the road. It beats my old 94 2500 ex cab with 350 and 5 spd which used to get 12 mpg with a 3:42 rear. After changing the rear to 4:10 it jumped to nearly 14 mpg.

I tow a 30' travel trailer 6500-7000 lbs. loaded. I get between 8-9 mpg. I try to maintain at least 65 mph on the interstate and 70 out west. I suspect if I towed 55-60mph I could get 9-10 mpg using a light foot.

[tswartos]

jeff, do a search after u find out what your gearing is. dont forget to check what type tires you have as this can affect your calculations and performance.

based upon what u said thats sounds pretty close to what i get. the main difference between the two mpg comparsions is that the gasser can and will get worse gas mileage. you stated yourself that u were pushin the speed limit and that burns up your mpg gains from the diesel. pulling a similar load last month thru the rockies i found i'd get 13mpg by keeping the rpms in the 1900 to 2100 range if i got to feelin froggy i'd get 11mpg...9 if the kid was screamin ;)

in town driving or interstate driving...your foot and the rpms u run it at affect your mpg. read some of the past threads on mpg and that wil give you the backround u need to understand how to drive the truck to achieve your desired results. when i first got my 6.5 i rodded it pretty good as it has such robust power...but as i pulled up to the pump one too many times i started to read thru other experiences and foud that my daily driving habits need to be adjusted. I thought about a gearvendors to add gearing to my tranny but for what I use the truck for it was an unnecessary expense...

so...assuming a stock configuration, the results u want is directly controlled by your foot. anything more would require some modifications or a duramax. simce u opted for a 6.5 i'm assumng that a duramax was out of the picture for a while. remember this is a light duty diesel that shouldve had a better water pump, exhaust system and an intercooler.

[ 08-20-2003, 01:19 AM: Message edited by: tswartos ]

[jeffreydmet]

I also have been disappointed with the apparent power that my 6.5TD appears to have in the mountains. I swear the 350 gasser K3500 I had before the diesel pulled at least as well in the mountains with the same loads. Of course I had to keep the RPM's up on the gasser. Perhaps it was the manual tranny on the gasser that made the difference. The diesel has an automatic. This is the first time I have ever pulled with an automatic an I hate it over the manual. I am considering swapping it for a manual. Maybe the manual would help with mileage also.

[LanceW]

for what it's worth, I pulled our 3-horse gooseneck (prob. 6,000 empty, 8,000 w/ 2 horses) from richmond to Ithaca to Hartford back to richmond and got just under 11 mpg this weekend. Trailer has frontal area of a barn door, and I kept it around 65-70 mph on the interstate. 4.10 rear, 3500 dually, A/C on all the way. You can never be sure, but I would bet against a gasser doing that well. Hard to make a good comparison unless you have two trucks side-by-side on the same route with the same load.

usually get 14.5-16 empty, depending on how heavy my right foot is.

[catmandoo]

geez mileage like that i'd end up in the welfare line if i don't get at least 25mpg with my 6.5 i'm ****ed hoping with the turbo should give me a couple more and maybe a gearvendor and i should be over 30 i drive a 92 ext cab 2wd with 5spd and whoever said watch the rpms is correct if i drive between 55 and 60 i can run 26-27 if between 60 and 65 it drops to 24.5-25 and if i run 70 it drops to 23 or so.also when i put a topper on it i gained 2mpg so if your running bumper hitch that could help a little.

[oldmansax]

We all need to do whatever CATMANDOO is doing!!!

I was disappointed with my fuel mileage too. The worst was 10.5 & best was a smidgen over 14... & that has been empty, loaded or pulling anything from a lawn mower trailer to a lowboy with an excavator (15000+ plus the trailer). The good thing is I got 6 MPG with a 454 gas I used to pull the excavator with. The Dodge does get better fuel mileage.

[Marty Lau]

JefferyDmet;

Let see you got a crew cab one ton and pulling a trailer at 75+ mph.........now wonder you mpg is low. I would bet you have 4.10 rerar end ratio or maybe even 4.56. You will get your best mpg driving at or below 1900 rpm. Rule of thumb for every 5 mph over the speed 1900 rpm gives you you will lose 1 mpg. So if 1900 rpm gives you 55 mph then driving 75 mph will cost you 4-5 mpg. You can either SLOW DOWN or change the rear end ratio.
I have regular have gotten empty 19.5- 20 mpg at 75 mph but I have an short box extened cab 2X4 and a improved exhaust and went to 3.42 ratio. Now any thing over 5-6,000 towning is workout for the truck. I have towed a 26 foot and 27 foot bumper pull campers over 1300 miles through the mountains and have gotten 14.5 mpg to 10.5 mpg. The lower was pulling 75 mph and I did that once and the truck worked too hard to keep that pace and I found that at 65 mph my truck towed nice kept the RPMS around 1900 and mpg between 12- 14.5 mpg. The 6.5TD produces max tourque about 1900 rpm any faster you pay with more fuel. If yo have stock exhaust getting rid of it and going to an good after market exhaust will give you about 6-8% increase in power and economy by changing gear ratio from 3.73 to 3.42 and going to a good exhaust I picked up 12%on my mpg.
The 6.5TD replaced a F-150 2X4 5 speed gaser that never did better than 14 mpg empty and comutting and round town 9 mpg so the 15-16 mpg around town and comutting I get with the 6.5 is alot better.
If you had a one ton crew cab with a 350 gaser doing as well as the Diesel you had an exceptional truck before.

[BuffaloGuy]

You all might find this interesting.

Test between a '99 454 vortex (or whatever liter they call these things) and my '93 6.5 bone stock. I purchased both these trucks new. Both heavy duty 3/4 ton extended cabs.

Both had a manual trans. The 454 had about 25,000 miles on it and the 6.5 about 90,000 miles. Both trucks bone stock, same rear end (4.10), same day.

We pulled empty stock trailers (goosenecks) on I-80 and state hwys. from Laramie WY to Greeley CO, loaded up and came back.

The pull out of Laramie is pretty good and reaches the highest point of I-80 coast to coast. Not that high, but nevertheless a pretty good pull. I see lots of big rigs pulled off to the side of the road panting.

Both trucks had radio contact so we could test lots of factors.

With the empty trailers, both about 3500 lbs, the 454 could out pull the 6.5 - just barely. The 454 was faster off the line. (Who cares about that?)

RPM per ground speed and gear was exactly the same.

Then we loaded.

The 6.5 got most of the weight about 2000 lbs. while the 454 only got about 1000 lbs. We were moving a hand to the ranch so the loads were light.

Now loaded, the 6.5 would literally walk away from the 454 and had to wait for the 454 at the top of the hills.

On the flats the 454 had it to the floor to even keep up with the 6.5 which still had plenty of throttle left.

Then we filled up. The 454 got 7 mpg the 6.5 got 15 mpg. The guy who drove the 454 was not a 6.5 fan. He is now.

From past experience we have found the gassers get about 100,000 miles pulling heavy until they are done and my 6.5 got 185,000 pulling even heavier loads until it quit.

My 6.5 bone stock would get 12 mpg pulling 20,000 lbs, 65 mph at 7500 feet.

15,000 lbs or less it would get 15 mpg.

Empty at 65-75 mph it would get 18 mpg.

Empty at 55 mph it would get 20-21 mpg.

Now it has a new motor and I haven't had a chance to really test it yet but it seems that I have more power but poorer mileage. Too early to tell.

Overall, you need to drive a diesel about 100,000 miles to get the savings in fuel vs the the added motor cost out of it. After that the fule savings goes in your pocket. If you don't pull heavy loads a gasser is better.

A 6.5 is a light duty diesel engine that will out do any gasser on the road so long as they are both being worked hard.

I made good money on my initial investment for the diesel motor upgrade when I bought the truck new in 1993. Over the last 10 years I saved hundreds of gallons of fuel and got about double the miles out of the motor vs. a gasser.

Now I've spent about $10,000 getting the whole truck redone (new motor, tires, tranfercase, alignment, new gear fluid etc.). I expect to get another 200,000 miles out of this. Maybe more since this motor addresses some of the factory problems that the original had.

That is about as good as trucks get. It's not shiny. It has a few dings but is runs like a top and everything works (except the a/c).

If I had money to burn I'd buy a Duramax and drive it for 200,000 miles plus but right now were in a drought and times are tough so you make do best you can.

That's how I look at it smile.gif

[cruzer]

I have a C2500 auto w/4.10's w/a 2000lbs slide in and 5000lbs car & trailer traveling thru the hills of KY/TN going 70mph @ 2500rpm Im getting about 11.5mpg, at 75mph it drops to 10 or a little under. The beauty is I get minimal fluctuation of speed when pulling hills. I pull w/friends w/small gas motors and the are really pushing thier trucks hard to keep up. Their mileage is close but not better. B4 the mods I would have to hit it pretty hard to go fast. A guy I pull w/has A 2000 K2500 big block auto w/3.73s he pulls a lighter car and trailer(4000lbs),no camper.On hills and most of the time, Im on his *ss until he has to stop for fuel, or he decides to go 75+mph. I can go that fast but don't see the need. I'll evetually catch him anyway. His truck seems to work harder than mine w/the same load.It downshifts frequently because of the gears he has,mine rarely does. You also have to keep loose clothing,small kids & birds away from his intake on acceleration. Sounds like they might get sucked in.

[GARY PAGE]

I get above 20MPG unloaded with my 95 1 ton dually and above 15MPG when pulling my race car enclosed tralior approximately 7500 LBS in TN. I drive by the Tach and put the RPMs at 2300 which is about 68MPH with my oversize tires and boost is 5PSI. My gear ratio is 4:11 but the tires make it look like a 3:73 and it a new engine. Air filters, Fuel filters, oil filters and oil changes are critical to the MPG towards the end of a cycle. No cat, no muffler and 3" pipe all the way back. Air box mod and intake mods and it breaths real good. I turn the cruse off run like heck down the hill back off comming up like the big trucks.

[DogDiesel]

I like my pulling mileages.
93 6.5TDA low compression, marine pump & hi-pops, Peninsular non-wastegated turbo, intercooler--blah-blah...
I have four trailers, a 24' GN equipment hauler, a 18" GN horse traler, and a 18' flat-bed bumper pull and a 36' fiver Avion RV.
18' flat-bed empty 16.5MPG, 15.5 loaded. with 4K (trl wt - 1850lbs)
18' GN horse similar (trl wt 3300lbs)
RV gets 11-13 IAW speed.
24' GN (wt - 4400lbs) got 14.5 towing empty trl.
Then I (really) loaded the GN. Gross weight (overloaded) of truck - trailer and load was 28,400 lbs. Truck got 9.26 MPG measured over nearly 1000 miles. Not bad, this is quite a testament, not only to mileage, but even pulling the load. Pulled 0-40 too EZ on take-off and cruised at 60-62 MPH, 7% five mile hills pulled in 3d at 40+, all without even high temps, and 9.26 MPG.
No gasser can do that.
Wayne
BTW-Till I put a 3d axle under the 24GN, neither will I again...

[jeffreydmet]

I have changed the ratio in my differentials from 4.1 to 3.73 and put on 285/65 tires to give the equivalent of 19% over stock. I have also corrected the VSSB so that the speedo reads correctly. At 70mph my engine now runs just over 2000 rpm. On level ground like crossing I-80 in NE it still easily pulls my load in OD. The gear ratio change added perhaps 1mpg empty. Not what I expected. I haven't done anything to my exhaust yet except check the back pressure which seemed to be within spec. Its not too expensive a mod but I want to be sure it adds to the economy.

[moondoggie]

Good Day!

I bought my '95 pickup 2 Jan 2000. It has 4.10 gears; it's bone stock. It had LT285/75R16 tires when I bought it, which meant I had to correct my mpg's by ≈ 1.08 (standard tires for my truck are LT245/75R16's).

No-Load mpg

Worst, 00 winter -------- 17.6 (1st 5 tank rolling average calculated - mpg went up after this)
Best, 00 summer --------- 18.9 (occurred in Apr & May, dropped with A/C use)
Worst, 00/01 winter ----- 16.0
(installed LT235/85R16 tires, mod. VSSB, 8 Mar 01)
Best, 01 summer --------- 19.4
(installed GV ≈ 1 Aug 01)
Best, 01 summer --------- 21.3
Worst, 01/02 winter ----- 18.3
Best, 02 summer --------- 20.5
Worst, 02/03 winter ----- 17.7
Best, 03 summer --------- 21.0
Worst, 03/04 winter------ 17.4
Best, 04 summer --------- 21.4
Worst, 04/05 winter ----- 17.9

All mpg's are 5 tank rolling averages, to eliminate single fill-up variations. All mpg's are either corrected for odometer error, or VSSB was modified to make odometer error < 1%. All mpg's are no-load: truck empty & pulling nothing. "GV" above is the Gear Vendors 78% Auxillary Overdrive I installed. With the 235 tires & the GV, my effective ratio is 3.08.

Trip mpg's

Jul 00 Cleveland, OH ----- 20.0
Jul 00 Williams Lake, BC - 17.8
Aug 00 Chicago ----------- 19.9
Mar 01 W. Virginia -------- 18.7
Jan 03 Cleveland --------- 19.5
Jun 03 L'Anse, MI -------- 22.5
Jun 03 Muskegon, MI ----- 22.8
Sep 04 Longville MN ------ 23.0

All trip mpg's are also no-load: truck empty & pulling nothing.

Pulling mpg's

In the 2000 - 2002 summers, I pulled a US Cargo SM625TA2 trailer
www.uscargo.com/uscargo/products/enclosed/snowmate.asp (http://www.uscargo.com/uscargo/products/enclosed/snowmate.asp)
(- then click

[Marty Lau]

I think you would find with a good exhaust you would pick up another 1 mpg. You need to get rid of the down pipe it has about a 45% restriction built in and hurts economy and performance particular when you tow and have high power demands. (more exhaust flow)

[moondoggie]

Good Day!

I forgot to add that that's one of many things I'd like to do to my truck. In fact, I'm thinking that opening the air intake up (like JK showed me on our '95 Sub), then exhaust, gauges, cooling mods, chip, ...

Blessings!

Brian Johnson, #5044

[LanceW]

Buffalo Guy nailed it when he called the 6.5TD a light-duty diesel. If you look at kelly blue book values, a '00 3500 6.5TD is worth around $13,000, and an '01 Dmax is worth around 24,000. Why the difference? Because the 6.5TD is a light-duty diesel in what has become a medium-duty market.

If you can live with the 6.5's shortcomings, it is a great value. In my case, the '94 is paid off, now pulls less than 10,000 lbs, is no longer a daily driver, and we only run it 15,000 miles/yr. It does everything I need and does it better than a gasser could. (though I can't seem to get 25mpg, everything must be downhill in IA ;) )

If you need to pull as heavy or fast as the other rigs out there, you'll need to either mod it a bunch or get your wallet out and go to a dmax.

[jeffreydmet]

No body has said much about the difference between a manual tranny and an auto. Does anyone have an idea about how much mileage the auto waste. When I was in the mountains and had to shift into 2nd to get up some steep hills I noticed that the torque converter would not lock up and my speed would drop about 30% over running the same rpm on the flat.

[DogDiesel]

I towed with my previous truck (lighter duty) and I swore it would be my last automatic for towing. Changed rear gears, and it still made heat.
I will stay away from commenting on how much power is lost, because without measurments, side-by-side tests or factual calibrated data, it'd be just opinion.
The manuals make for less heat and put more power to work. Sure, the automatics are better to drive in traffic, but when pulling...
Why not just look to our bigger pulling brothers, the truckers, count automatics and count manuals. Sure there are automatics that can pull loads of most any size, but O.T.R trucks run standard. HMMHM.
But as the gentlemen stated above, most who own the trucks with 6.5s pull lighter loads, or use them as daily drivers, so most of this is mute.

I think the manual tranny is key to my truck pulling well. And I am a long way off from considering trading. I've drove them--the new trucks-- towed with them, and no payments and doing the same job will keep my "dog 6.5" around for a while, possibly until the next generation after the Duramax and the F**D & D**GE.
Wayne

[catmandoo]

no lance everything here in iowa is not downhill but if you stay north of i-80 most of it is pretty flat nothing like nebraska though. today i ran west to east round trip 300 miles,on a different note yesterday ran south for 130 then back north and ran 24.6 at 55 to 60, today ran east and back and have yet to calculate but by the gauge i'd say 26.5 to 27 and ran 60 to 65 what i did different is i have a keystone dual scoop ram air hood like old 70 442's well i took the factory air hook up off the fender and put an elbow up to the hood for cooler air seems like i don't need to push down on the pedal as much as i used to and if you look inside the muffler on the air intake you'll see it restricts air flow probably in half. diesels love air flow now i just need to get a good seal against the hood and at 65 to 70 it should give me good flow like a turbo we'll see i'll keep ya posted .also since doing this my temps have dropped probably 15 degrees

[pgoldstein]

I would like to know what the trick is to get over 14 mpg. I have a 97 4X4 Crew Cad Dually automatic with 4.10 gears and slightly oversized tires. At 70 mph I am running about 2300 rpm in O.D. with the converter locked. I have checked my mileage several times and adout 13.5 is as good as it gets at 70 empty. I wonder if my stock exhaust and cat with 140k miles may be the cause.

[BuffaloGuy]

Hey catmando, tell us more about your cool air mods. Got some pictures?
Ken

[Dvldog 8793]

Howdy
At the risk of being redundant redundant redundant I would like to agree with everyone in saying that 1900 rpm is the key. My truck gets between 18-21 mpg unloaded at 75 mph. That's around 1900 w/ my Gearvendor OD. If I run at 60 in 3rd w/ the gearvendor I get about 24 mpg at 1900. I think wind resistance makes the difference. The worst I've ever got with a load was 11mpg, that was about 18,000 pounds of goose neck with ALLOT of wind resistance on a 80deg day. My truck never runs hot. Never seems to be lacking in power. Rides like a Caddy unloaded and a like a buck board loaded. I have had all different combinations of gassers/trans over the years and think that you'll be hard pressed to beat the positives of a diesel. I have never had a gasser that top my diesel in loaded pulling grunt/mileage or unloaded mileage. That includes a "90 chev short box 2wd V6 stick. The only up side to a gasser that I can think of is "excessive speed of excelleration" :D (that's what my many tickets used to say) I had SS454 that would smoke the tires till the rubber was gone, never been able to get my 8000lb 6.5 to do that!
BTW: "99 chev 3500 265 tires, CC LB SRW, 4.10r, 4x4.
BTW2: The best thing I EVER did to the truck was open up ALL the exhaust. gained 2 MPG and incredible HP gains.
Hope this helps!
L8r
Conley

[LanceW]

catman- just pokin' at you! With a 5-speed, good airflow, and takin' it easy I have no doubt at all in those numbers. Tell you the truth, I'm always amazed at what these 6.5's can do if you put a little into them.

Man. tranny is definitely best for long-haul truckers. The reason the manufacturers recommend autos for towing in light-duty trucks is that they are more often used locally over short distances. They figure the torque converter (designed to slip) is better and more durable for stop-n-go than the clutches in light duty trannys, or at least that's what they say

[catmandoo]

well to tell ya this is the first stick i've had since my 65 442. the guy that bought this new bought it for a company truck he put on 1200 to 1500 miles a week and wanted the best milage he could get. and thats about what i put on after today i'll have 1500 this week the only real problem i encounter is when i drive momma's suburban on the weekends i'm always goin for the clutch pedal she just laughs at me.around town drivin can be the pits some days in stop and go traffic but i notice i have a tendancy to go slower and try to time the lites so i don't have to stop,cars might build up behind me and bitch but if they really got to thinkin they are saving gas by still rollin but they're morons that go like hell from one lite to the next and think they're getting whereever faster.i guess it comes down to time is money the faster you go the more it costs ya.as for my intake mods ya can't have a pic yet i'm not done but i think the first thing to do if you still have that factory muffler between the fender and aircleaner is throw it away it has a restriction in it down to half the size of inlet.when i bought my hood i could have bought the ram air box but they only make one for the gasser 350 discrimination i say.but then they want 170 bucks for it so probably a good thing they don't make one. i'll try to get some pic's when i'm done

[Kidd]

I used to think that a manual was the best for heavy haulers.. till we got a couple of new tractors for hauling gravel at work. These are 410 hp Mercedes diesels with a 5 speed Allison.
These things pull 80,000 lbs. out of some pretty steep holes better than the older 450 hp Cummins
coupled to a 15 speed manual tranny. The guys just hold the rpms at about 1900 and cruise up the hills. On an average day, they make an extra trip over the manuals.. mileage is much better too. Smooth as silk shifting.. almost impossible to tell when they shift gears. That Mercedes is sure quiet too, makes less noise than my 6.5.
Hmmm.. wonder if I can shoehorn it into my GM...?
:D
K.D.

[BillCarry]

Got a '94 front engine 6.5 TD motor home. Weighs about 14500 all the time. Consistently gets 11.5 to 12 mpg on 3-4000 mile trips. Checked this about four times going to Florida and back. Had three gas motor homes before this - all got 7-8 mpg doing the same trips. Two were Dodge 440s and the third a TBI Chevy 454. The first three were smaller and weighed about 13000.

[DogDiesel]

This is an interesting thread.
Having monitored this forum almost since its beginning, the mileage figures posted in this thread are lower than those boasted in years earlier 6.5 forums here, and more believable.

I used to wonder: Are my driving habits too agressive? Is my truck not set up optimum, cause at one time, few years back, one-tons with 4:10s were getting 19-21 MPG and I just never measured up. This concerned me, until I was on the TD* (DOD*E)formum and people began to brag, and mileages got better and better, (24, 25MPG) and brag. Till one guy was regularly getting 27.5 MPG with a 3:54 4x4 Cu***ns and--boy my 6.5 was just a dog...

("most fisherman are liars cept you'n'me and sometime I doubt you...")

I don't believe my truck could be set up much better to still pull and get anything like decent mileage MORE, and while it is capable of getting 17.5 + or - 0.5 MPG, it rarely gets it, and ironically, it can get almost the same mileage towing a light trailer; redeeming the theory that it's simply RPM and gearing. That mileage empty is about 16.5 and since I listed my towing figures above, they're there.

As for the question of why you cannot get above 13 or 14, mine got those figures too, until I cleaned up the breathing by removing that air induction blockage in the fender, and put larger exhaust. My timing gears improved mileage, some too.

As for difference in automatic and manuals, its a MPG or two + or - about 0.5MPG.

And my apologies. As for my comparative comments about OTR trucks which was replied and compared to local running dump trucks...maybe I should have said long-haul OTR. Sorry. Of course an Allison is better for local heavy dump and delivery, garbage trucks etc, it saves the drive train, and heavy local autos do probably get better mileage, for truck accelerating and slowing in traffic.

To comment on the concern and classification of light duty engine or medium duty engine...That rating relates not on the ability to haul loads, but the longevity documented based on average time to rebuild, for medium fleet haulers. Since OEM 6.5s in general lacked the torque, HP and especially cooling required to power up fleet haulers, it is and always will be known as a light duty engine. But too, one tons and less are light duty.

Again, great thread.
Wayne

[catmandoo]

dogdiesel you are correct on that fender resticting air intake i used to think that was just a muffler to dampen intake noise til i took it off and looked in there heck my john deere lawn mower would lose power sucking thru that thing.i think some of my good milage comes from keeping it at a reasonable speed the only time your gonna get good milage at 75 is downhill i don't care what you drive.if ya want to drive 75 fine but its gonna cost ya i recently went to california thru colorado and there were people literally flying up the mountains i on the other hand was lucky to get 55 sometimes.i'm sorry but i won't beat the hell out of my vehicle like that so it takes me another hour or so to get where i'm going the trucks still in one piece ran cool and got pretty decent milage i'm happy and my trucks happy and thats all that matters

[jeffreydmet]

You guys have pretty well convinced me that I need to work on my exhaust. As for power to be gained I did some back pressure test and did some calculations that the engine is wasting 6hp pumping the air past the restriction at full throttle. I cannot estimate the power gain from the cylinders exhausting better. As far as the breather inlet restrictions I can work on that too. What have you guys done specifically. Whatever I do I don't want to spend more money and not get a return on my investment.

[BuffaloGuy]

Yup, jefferydmet you made a good thread. Not bad for a newbie. (don't you hate being called a newbie?)

I'm hearing talk about an intake muffler that is robbing power/economy. Maybe I'm blind but I can't find one on my rig. Did they all get one? Anybody got some pics?

Mine is a '93. Does it have one?
Ken

[Tough Guy]

Something that no one has touched on is additive.

I drive 150-250 miles a day. I use Power Service with a cetane improver of +6 and have seen an increase in mileage, enough to pay for itself while also gaining the peripheral benifits such as pump and injector lubrication/cleaning.

For what its worth...pulling 10,000lbs I get 10-13 mpg as others have said by watching rpm/speed.

My 6.5 has 118,000 hard miles and still runs like a top. No gasser will give comparable service this late in the game.

Cheers

[Marty Lau]

WOW!!!!!
Folks this is a Great thread packed with good info, I for one appreciate the gasser Diesel comparision that The Buffalo Guy made, it is rare you get a side by side comparision. The detailed info Moondoggie gave thanks for the time! Catmando showing us if you clean up the exhaust and intake what is really possible with a 6.5TD and I believe his info as I have seen close to 25 mpg several times when I have been empty and not in a hurry just cruising a modest speeds. Chris made a good point about fuel aditive which I use every fueling like him just becomes habit and don't think much about it.
Jim (MOREPOWER) used to write about the need to gear for the speed you wish to run and a quality fuel aditive and the benifits. I think it would be a benifit to newer members if Jim would from time to time republish some of the past writings.
Kind of a best of. Or if the new members purchase past articles and ad them to their reference shelf.

[catmandoo]

buffalo guy mines a 92 and it's between the fender and air cleaner big ugly thing like used to be on the old 5.7 olds diesels.

[Laffman]

I got to do a side by side comparison, so to say. The drummer in my band has a '98 K3500 with a 454 gas engine while I have a '95 C3500 with a 6.5l Diesel. We had a show in Toledo, OH. We're from the Detroit, MI area. He wanted to drive on this trip. We have a 8x5 trailer we haul the equipment in and it weights in at about 2300 lbs. He went thru an entire tank of gas just to go from Detroit to Toledo and another tank to get back. When we had a show in Chicago, we used my diesel. Pulling the same trailer, I got the same mileage I get without the trailer, 13mpg. I was able to get to Chicago and part way back before I had to fill up again.

In another "test", the whole band went up north here in MI one weekend. My drummer decided to bring his 29' Cigarette boat, weighting 9000lbs, with him. He pulled it up with his K3500 and went thru 2 and half tanks of gas getting there. He decide to let me pull the boat back to see how my diesel would do. He's not a diesel fan, he's more concerned with how fast his truck can be verses how well it can pull. I made it back on a single tank of diesel and still drove to work for two more days before I had to fill up again.

This completely convinced me that I made the right choice in getting a diesel when I got my dually. A gas engine just can't compete with it.

[BuffaloGuy]

Hey catman. Mine is a '93 and I don't have anything between the fender and the air filter. I guess they quit putting them in in '93?

[rjschoolcraft]

I average 8.0 mpg towing an 8000+ lb. travel trailer (GCVW of 16,500) running 70 mph. No mod has made a bit of difference. I run Stanadyne Performance Forumula in every tank. I get 15.5 to 16 mpg solo. I should probably slow down to get better numbers.