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How to get better fuel economy w/your diesel



  • KCRamKCRam Mt. Arlington NJPosts: 3,516
    Totally correct. This is why tractor trailers cover their grilles in winter - it's the only way the radiator will maintain heat.

    kcram - Pickups Host
  • John,Here in Rock Hill SC it does not get as cold as St Louis. 18 to mid 20s for lows is about as bad as it gets except maybe a week in January were we might see a couple of nights near 10 degrees. But letting the truck warm for about 5 to 10 minutes will clear the frost and ice off the windows . The air from the vents is warm but not hot and the temp gage will be in the lowest part of the normal range. It takes about a mile of driving for it to get fully warmed up to normal temp.
  • jim314jim314 Posts: 491
    "Cummins Engine Co. states that it is three times harder on an engine when idling than pulling a load down the highway. It is much more economical to purchase a generator or a diesel-fired cab and engine heater than to idle your engine. Diesel engines are not built to be used as heaters."

    The preceeding quote was in reference to large truck diesels, but Mercedes did offer an axiliary diesel fuel heater in their Sprinter van. Of course, it may in fact not be worth it to go to the trouble and expense of buying and installing a generator or diesel-fired cab and engine heater for the few days you might really need it. I am not familiar with these auxiliary heaters, their cost and maintenance issues.
  • Thanks alot for the info. May I ask again what year your your super duty diesel is? Also if you dont mind may I print your reply and use it in my arbitration case. I need to show Ford that my '08 is not functioning properly comparing to other '08's. Ford has since come back to me since starting the arbitration saying that my 5 check engine lights for low engine operating temperature warming problem is NOT a problem and my truck is run correctly. I do know that my 2005 6.0 diesel would warm up just as you explained your is warming up, and my '08 is just the opposite.

    John W.
  • Hi John, My truck is a 2008 with the 6.4 diesel. Yesterday I took it to the dealer for a oil and fuel filter change. I spoke to the mechanic about letting the truck warm on cold mornings . His opinion was that its not a bad idea to let one warm up for a few minutes before driving off. He is one of two mechanics certified to work on the new 6.4 at this dealership. I don't mind you using my reply in your case. Do remember that the 6.4 has a total of 6 different radiators to keep things cool. The main radiator is about 20 percent larger than the one in the 06. So the 08 is naturally going to take longer to warm than the 06, but it should still warm up some. I will agree with some of the other post that a block heater in colder climates may not be a bad idea. They are not to hard to install and some will install in the radiator hose line. Several years back those were about 80 dollars, I have not priced one lately. Hope this helps Frank
  • Ford does offer an auixilary cab heater and engine block heaters on their 08 trucks.Neither option was that much, I believe the cab heater was around 200 dollars and the engine block heater was around a 100 dollars. If I had done a factory order I would have got both options. however the main option I wanted was the in dash nav system and their were only 5 trucks within 200 miles of me with the nav and the color that I wanted and none of those had the cab heater or block heater. While I agree that letting a truck idle for 30 minutes to an hour is excessive I consider a five minute warm up in cold weather to be a normal warm up time. To not let it warm up enough to clear the windows is both illeagle and unsafe. While I haven't had experience working on truck diesels I have had experience working on standby diesel generators every thing from a 5 hp pull cord up to a 16 cylinder 8 turbo 10 thousand horse power unit with a 17 inch bore and 21 inch stroke that sips fuel at about 43 gallons per minute. Each of these were set to run at idle for 3 minutes to come to operating speed and temp before engaging load and after running under load each was set to run at least 10 minutes no load to cool down before shutting down. Ford recommends at least a 3 minute cool down on the 6.4 to cool the turbos after running under load. All of these engines would be 15 to 30 years old today so I can't say what a modern cummings engine would do but the ones i used to work on would generate heat and a lot of it at idle.
  • My '07 GMC Duramax w/ 15k miles gets a dismal 13.7 mpg max. It doesn't seem to matter if I am driving in town or on the highway. If I'm towing, it goes down to 11 mpg. That doesn't concern me as much as the absolutely awful gas mileage on average. My [now probably in Mexico because it was stolen] '03 F-250 got 18 mpg in town/22 hwy, so this was a bit of a shock. I waited not-so-patiently for the engine to get a few thousand miles on it, thinking the mpg would improve, but it hasn't. With diesel prices at this hour $4.59/gal. here in the SW part of NM, I would like any input on chips that might improve gas mileage. I'm not interested in more HP or torque. Am I dreaming?
  • I have the Ford 2008 F250 Lariat Crew Cab 4X4 short bed with the 6.4 Diesel. I've owned it for about 3 months and have 7500 miles on it. The new diesel engine/exhaust is programmed by the factory to go into a "soot burn-off" mode whenever the exhaust soot collector starts loading up. On my truck, I've noticed the burn-off happens about every 300 miles. During the burn-off period (usually about 15 miles of hiway driving) the MPG will drop down to about 12mpg. After the burn off period is complete, the MPG pops right back up to its normal value. For my F250, that's about 18mpg on the hwy at 65mph.

    My Ford dealership was unable to explain the 12mpg when I asked them about it, so I had to do some investigation to figure out what was going on.

    As for the fuel mileage trend while the engine is breaking in, I've kept pretty good numbers on my mileage, and 90% of my miles are commuting between Arlington and Seattle - a 100 mile round trip at freeway speeds. When new, my truck got about 14mpg. Now, with 7500 miles, I'm getting about 18mpg. This drops to about 15mpg when I'm tooling around town. I expect that mileage will continue to improve another MPG or two as the engine breaks in...

    As a comparison, I traded in a gas 5.4 Triton 2005 F-150 that was getting about 16.5mpg doing the same type of driving. Doing the math, it costs me 27cents/mile to drive my diesel F-250. It cost me 25.5 cents/mile to drive my gas F-150.

    Am I happy with my diesel performance? Yep! Still trying to justify a chip. If I could find one that has proven increase in MPG without playing with the fuel injectors, I would be interested. I'm pretty sure that the only way to improve gas mileage is to tighten up the shift pattern. :shades:
  • jonbyrdjonbyrd Posts: 1
    Hey..people..have you ever heard of running a car on water.?

    This is true,Why should we bother thinking about how to increase the mileage of the car using diesel.Even if we can increase the mileage its is still costly for us ,As the prices of crude oil are increasing day by day.So we should think of making a few alterations to the engine.We can run the car by the electrolysis of water producing Hydroxy gas.This is what called as HHO fuel.Lets think of it once.I have also seen some useful information in the site

    I have given this idea because I have seen some of the people in the above posts saying that Its costing them a lot at a very low mileage and even the mechanics are charging a large amount of money.

    I'm expecting a great milage at low cost using the HHO fuel
    I hope you get what am saying.
  • Hello Everyone,

    I just joined this website after first researching hybrid cars etc. then fuel cell vehicles, and came across a site that said water could be used for fuel. :confuse: My husband and I have a 2006 350 Ford Super Duty outfitted "to pull a house" bought with the intention of pulling a really big fifth wheel now used to pull a horse trailer and bought when diesel was "cheaper" than gas. Our other vehicle is a 2002 little Ford T-Bird and that is not fuel efficient. Our truck gets 14.9 miles per diesel gallon even not pulling. :cry: Any thoughts on this??????????????

  • jim314jim314 Posts: 491
    The water fuel claims are bogus, and the sites that promote it are a scam. Water contains no net fuel value. It requires more energy to electrolyze water to split it into hydrogen and oxygen than you could gain in hp when the hydrogen is fed into the hydrocarbon fuel stream.
  • Hello Jim314,

    You have of course converted a diesel or other vehicle to using water??????????????? The conversion "kits" seem plasible. They are inexpensive so who out there has actually done the conversion and what are the results????????????????
  • In my opinium injecting water into a diesel is a big mistake and the repairs could be very expensive. A good web site to go to would be, then to their research and development site then hydrogen fuel info. These guys have been working on a hydrogen fuel conversion kit and hydrogen generator for quite some time. per them diesel will not run on hydrogen.
  • jim314jim314 Posts: 491
    One has to be properly skeptical of all engine add-ons which are claimed to increase fuel efficiency. In the specific case of the electrolysis units which produce a miniscule amount of hydrogen and oxygen gas, there is no generally recognized scientific or engineering theory whereby they could do what they are claimed to do.

    If they really did work as claimed, then they would be available from the vehicle/engine manufacturers, at least as an option. The purveyors of these devices are not bound by an ethics policy to conduct accurate and unbiased studies showing that they really do work. They cite unreliable anecdotal accounts as evidence that these devices work.
  • jim314jim314 Posts: 491
    The hydrogen enrichment devices currently available produce a miniuscule flow of molecular hydrogen and molecular oxygen, but the purveyors are claiming big benefits without any research to back it up. They cite research done at the US gov't Idaho National Laboratory, but that research does not support the claims of any benefit from extremely low levels of hydrogen enrichment.

    For example, one company is currently selling their brand of hydrogen enrichment device for installation on large diesel trucks (over-the-road tractor-trailers, I assume) and diesel school buses. The unit is an electrolysis unit which sells for $7800 plus installation charge of $200, so $8000 installed! The company reports that the unit consumes two liters (2 L) of water per 10,000 to 12,000 miles! 2L of water weighs 2000 g, water is 11.1% hydrogen so this 2L would yield 222 g of molecular hydrogen (H2) over that 10,000 miles!

    What is the mpg of a large diesel tractor-trailer? 8 mpg? 4 mpg?

    Let's say 6 mpg. At that rate over 10,000 mi it consumes 10,000mi / 6 mpg = 1667 gal of diesel fuel. 1667 galUS is 6309 L times the density of diesel fuel, 850 g/L = 5,360,000 g of diesel fuel over 10,000 miles.

    So the added molecular hydrogen as a percent by weight of the diesel fuel = 100% x 222 g / 5,360,000 g = 0.0041 %.

    Such a low level of hydrogen enrichment has not been shown in properly controlled trials to have any beneficial effect. This is 1/100th to 1/1000th of the minimum amount of hydrogen that has been studied in hydrogen enrichment experiments. See

    I think it is money not well spent for some struggling shipping company or independent operator to be paying this much money for something which has not been tested in well controlled trials. The FTC should investigate these claims.
  • cotcot Posts: 1
    What gears did you get the 07 GMC??? My 2002 7.3L Lariat was also stolen two weeks ago.
  • joe183joe183 Posts: 1
    I have an '06 with 3.73's and the 6 speed manual. I was disappointed as well the first time I drove it finding such high RPM at highway speed. I had traded an '02. It had 3.55's and the NV 5600 tranny. The newer ones have the Getrag tranny. The difference is not only the lower geared rears but also the fact that the overdrive ratio in the NV 5600 was .73 and it is .79 in the Getrag. I felt I had no choice but to go to the Gear Vendors overdrive unit. I installed it in my garage with a buddy in about 5 hours. You will have to get the rear driveline shortened and a different yolk welded onto it.

    I still had the stock tires and at 70 mph I was turning 1800 RPM. I drove from Billings,Mt to Bismarck, ND at about 67mph (1700 RPM) and got 20.3 mpg. I definitely improved my mileage. Since then I have installed a Lorenz 2 inch levelling kit in front and went with 35 inch tires. Also a Ranchhand bumper. Now at 70 I am at 1600 RPM and my mileage is about 15 mpg. I have installed lockouts and only noticed marginal improvement. Between the lift and the heavy non-aerodynamic bumper and, most of all, the larger tires, I think my mileage has taken the hit. Bottom line is that you will improve your mileage with the Gear Vendors unit but stay with the stock tires or only a wee bit larger. The other option would be for me to run in 5th gear overdrive at about 60 (1700 RPM). In that case the torque multiplication is signifigantly larger than in 6th overdrive and my mileage would likely improve. I just don't have the patience.

    Lastly, I drove over the road for 10 years. Cats, Cummins, Detroits. You will notice that the peak torque on the Dodge Cummins is generally around 1600 RPM. That is where you will get the best mileage. The idea would be to run a slower speed at that RPM which is entirely possible with the overdrive unit. I wouldn't agree that one needs to "keep the revs up" to run one of these engines.
  • I also have a 2008 Ford F250 XLT Crew Cab 4X4 short bed, 6.4 Diesel with a 3.73 rear end. My first day of driving at approx. 65 mph, the vehicle averaged 9.3 miles to the gallon on the highway. One week later I'm averaging 13.3 on the highway at 65 mph. With a baseline of 65 mph on the highway, I've started researching various methods on how to increase my fuel mileage. My goal would be to reach or exceed 16-18 miles a gallon at 65 mph on the highway. Don't really know if this is due able but I'm trying. At this point Hypertech makes a programming device which will improve fuel economy by altering or tuning the motor for performance. So I purchased it. Additionally, I'm in the process of obtaining a new K & N Air filter that I believe will replace the stock air intake system on the twin turbo's. I guess my real struggle lies in the exhaust system or cat back. One person suggested I cut off the Particulated filter and run a straight pipe like a cat back. He said it will throw an error message but this can easily be reset. When I asked my muffler shop about this they encouraged me to keep the Particulated filter and just do a cat back. Any ideas on where to go from here? Or am I taking the wrong approach to this entire quest?
  • grbjgrbj Posts: 1
    Hi Fuel Economy for Diesels Folks
    I came to your site looking for better fuel economy ideas, and see a lot of you ragging on the hydroxy approach. I personally have two 30 liters/hr units installed because I do lot of heavy pulling w my '97 7.3 liter F 350. The truck is not even broken in yet [only 38 k miles] but the cost of the fuel is threatening my retirement plans.
    Since I am buying to equip a farm and develop property a hundred miles north, I do nothing consistently enough to develop a good set of comparative stats. But I do know many of you are not very well informed about what hydroxy purports to do. Let me make some points.
    I have read that it would take 3000 lit/hr to idle a small engine, so adding only two percent to the air intake is not a significant power source.
    1. Nevertheless, the addition of the hydroxy gas significantly increases octane, i.e., the number of the 8-carbon (chain) molecules in the fuel mixture. [FYI, methane is a molecule with everything attached to a single carbon atom, propane has three, butane four, and they all boil off the crude at different temperatures in the cracking/refining process. Any fuel is a blend of different percents of the different chains and related components, all of the pieces that make organic chemistry both highly complex and difficult. Thus adding pure (and purity is critical) acetone or zxylene to fuel in small quantities can really increase performance, or do nothing at all, depending on the mix in the initial blend.] Higher octane levels increase fuel combustibility.
    2. Regarding the energy used in its production, the hydroxy gas is electrolyzed with the extra alternator capacity for winch use, cold weather, et cetera, but otherwise dumped via grounding circuitry to prevent over charging and damaging system batteries at other times.
    3. Running the hydroxy gas through small water tanks has a double purpose. The water tank prevents random back charge explosions of the volatile gas in the generators themselves, but the various ions created in the [electrolysis] process also charge the water, letting its various vapors both aid in combustion and damp slow or late combustion, a task engine designers typically accomplish by feeding the engine an unnecessarily rich fuel mixture. Carbon fuels have become too expensive to be used partially as fire extinguishers, however much such mixtures simplify design for engineers and auto mechanics. Rich mixtures are necessary for starting and cold weather operation, but not leaning the mixture as much as possible the rest of the time is a waste of resources, especially in light Congressional calls for better CAFE [car average fleet economy] standards.
    4. But the ecu [the on board computer system controlling combustion, braking, et cetera] can void all the above by detecting the leaner combustion [increased oxygen, or manifold pressure, in the exhaust system] and upping its fuel mixture imperatives to the carburetion/fuel injection system. And federal law makes disabling on board diagnostic components illegal. Whether capturing sensor signals and attenuating them back to the levels the system expects, to sustain better system performance, is a grey area. Apparently the trucking industry has explicit permission from the federal DOT for such experimental modifications. But for obvious reasons, the ordinary citizen in his domestic vehicle does not. Nevertheless, the driver who does not monitor his systems and limit its unnecessary negative responses is just spinning his own wheels.
    5. So why have auto manufactures not installed such systems in new vehicles, or at least made them available as options?
    1) they are complicated.
    2) they require more maintenance than advertised.
    3) they expose sloppy users to significant dangers, i.e. explosions, chemical burns from catalysts, economic losses from faulty information about installation and use, et cetera.
  • dawsrtdawsrt Posts: 1
    Hi everybody, I'm new to this site so please bare with me. I recently purchased a new motor home on a Kodiak chassis with 6.6 duramax. I drove it home from Indiana to my home in Vermont averaging 8.3 mpg. Keep in mind that there is only 1,700 miles on it. I have asked several people how to get the best mpg and some tell me to drive on the conservative side and some tell me to drive it like I stole it. The idea behind that premiss i was told is to keep the engine as hot as possible so as to burn all fuel incoming to the engine thus increasing fuel economy. I will say that I had to do alot of mountain driving a few weeks ago, pushing it real hard and got 12.5 mpg on that outing. Is there anything to this theory or not I just don't know. Any advise would be appreciated.
  • KCRamKCRam Mt. Arlington NJPosts: 3,516
    Your RV is certainly heavy enough to give the Dmax the work it wants. But since it's new and low on miles, you do want to keep the rpm (and heat) up until it's broken in and the rings have seated. This is particularly important since I imagine you won't be driving the RV every day.

    Best practices during break-in:
    - downshift on hills, both up and sown, this keeps the rpm up.
    - shift the trans manually when possible, keeping the upshifts as late as possible (whether you have a stick or automatic)
    - if you're on an open stretch of highway, downshift and stomp on the go pedal... this keeps your speed safe, but gives the engine more work to do

    Once you've broken in, then you can drive conservatively.

    kcram - Pickups Host
  • I have a 2007 F250 6.0 ltre 2x4 crew cab at present I average 6.2 ltres per 100 klms .when my wife drives she gets 5.9 ltres /100 klms excellent to us. only added k&n filter system
  • I have a 2007 crew 4x2 6.o .I use 6.1 litres for 100 klms ( 30+ to a canadian gallon) I installed a K&N filter system and improved from 26 mpg
  • ingarageingarage Posts: 4
    I don't know if it's possible to do what I want to do. I may be taking a job that requires a lot of freeway time and the company will buy my fuel but they want us to drive vehicles that get at least 24 mpg, typically cars. I want to use a 1 ton dually because I need one to pull a 23,000# gooseneck 4 or 5 weekends a year (on my time). My business driving will be at 65-70 mph, generally level freeway near sea level in California. I would buy a used truck, looking for the right gear ratio and tranny, and would make whatever mods necessary to the plumbing and programming, plus tonneau cover. Probably 2WD to save weight and height. 1st choice is Dodge mega cab short bed, then 6.0 or 7.3 Ford crew cab short bed. Has anybody achieved this average freeway economy? 5.9 Cummins likely more economical than the new engine? Is 3.54 a good ratio for this speed? Advice on engine mods? Do I have to have a stick? Do dual wheels kill me? I don't know if I'd want to tow that much with singles, even a few times a year.

    I realize low numeric rear ends mean tougher towing with that big load. This would be at 55-60, so is there an automatic that will downshift to the right gear, or should I be looking at a manual? I'd go with an underdrive or overdrive if that give the most versatility. Again, I am willing to have an imperfect towing rig to get the high mpg unloaded.
  • jim314jim314 Posts: 491
    You're dreaming that with mods and option choices you can get 24 mpg with a truck that can tow a 23,000 lb gooseneck.
  • gagricegagrice San DiegoPosts: 31,110
    Just take the money for 24 MPG equivalent and pay the difference. I think 20 MPG is more realistic for a 1 Ton Dually.
  • It may be possible with an '06 or older Dodge Cummins. I had an '03 2500 2WD, and after getting broke in good, it was consistently getting 26-27 highway, running 75 mph. I then had an '06 2500 2 WD, and it got 23-24. Both of those had the auto transmission. I don't think the Fords get that kind of mileage.

    I then traded for an '08, because I wanted 4 WD, and that was a big mistake! I had to replace the catastrophic converter and particulate filter at 17,000 miles, and have never gotten better than mpg.
  • I have a 2000 Chevy silverado 1500. I haul 2 commercial mowers on a 6.5'x12' single axle trailer. The truck pulls okay, it has 173k miles on it though. I am going to buy a new truck, and thinking about a 6.8L v10 F250 (gas engine) I'm skeptical about the fuel economy though. I have no clue how much more I will spend in gas. Will a heavy duty truck with more pull power have close to the same gas mileage as a lighter duty truck pulling a trailer with mowers?
  • You can have a straight pipe on diesel trucks and pass state inspection. Diesels have dif than gas trucks. Yes it is that common. I dont know very many guys that keep the factory exhaust. And as for riding your bike a 2 lane country road.......what else do you expect???? I hate it when people do that. Thats why they have SIDE WALKS.
  • tvoltvol Posts: 1
    I was pulling my travel trailor when the turbo hose that routes back out towards the radiator had the clamp at the turbo fail. Since then I have lost about two miles per gallon according to the MPG display. Any suggestions?
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