Diesel Gas Mileage
#31
04-28-2009, 08:13 PM
Let's get scientific about this
First of all, I am relatively new (both here on this forum, and with Super Duty trucks), so please keep your flame throwers holstered. I am well aware of how wet behind the ears I am on the subject of these trucks.
What I’m a little more experienced with is the art and science of maximizing fuel mileage. I am an SAE engineer and am the founder and chairman of the National Hypermiling Safety Foundation, so I think I may have something (hopefully useful) to offer to the discussion.
I have 2K miles on my brand new, very first Super Duty (’08 F-250, 6.4 TD, crew cab, auto, 4X4, 18” wheels, A/T tires, 3.55 axle, Sunoco ULSHDF, no additives, tonneau, original March 2008 factory ECU firmware).
Here’s the part where you’re all going to jump on me, but hear me out (please remember, I’m writing this post for your benefit, not mine).
According to my onboard (stock Ford) fuel flow computer/accumulator, I drove a 2 mile stretch of nearly-perfectly flat (45 MPH posted speed) south Florida pavement today (with the weight of about 26 gallons of fuel on board) and consumed fuel at a rate 23.0 MPG.
It’s not the (apparently) high MPG number that’s important (nor am I bragging about it), it’s the fact that the test was done in a moderately scientific way (which is the only way any of you should be measuring your mileage). In short, I reset the MPG accumulator once I had attained the set 45 MPH test speed (with cruise control engaged), and read the final MPG reading once it stabilized for a minimum of 30 seconds (and before altering the speed in any way). I then repeated the same stretch of road going in the opposite direction with the same measurement method, and got the same result.
Okay, this is going to be a long post, so go get your beer, go to the bathroom, walk the dog . . . I’ll wait till you get back.
Here’s what I’m talking about –
You’ve got to be scientific with your mileage measurements. You’ve got to exclude as many of the variables that are outside your control, as you possibly can. Those variables will wreak havoc with the usefulness of your measurements.
A FEW WORDS ABOUT AVERAGES: Averages are only useful if you look at them over very long periods of time, or over a very large number of samplings. When you fill up your tank, drive, then fill it again and hand compute your mileage, all you have is an average. That average is only of scientific value if you drive EXACTLY the same trip profile between every single fill-up. That means the exact same route, speeds, number of stops, driving style, atmospheric conditions, towing situation, song on the radio [just kidding] Etc. Those are all variables which invariably change every time we drive. As such, those changes in variables will cause your computed averages to vary constantly.
That doesn’t mean that those averages aren’t useful. Log those averages somewhere, and maybe after several months or years of doing that, you will be able to plot those averages on a curve over time and see some trends which you can attribute to long-term trackable factors (i.e. change in age of truck, change in age of driver , where you may have lived during the life of the truck, improvements to traffic systems in your region over time, mods, changes in your lifestyle over time, changes in your work situation over time, Etc.). Those are the only things that tracking changes in average fuel mileage can really tell you about . . . long-term trends and changes.
SPOT LOGGING: No, that’s not what your dog does in the backyard. It’s actually the only way to accurately measure (a) the actual mileage situation with your truck, and (b) help you find your truck’s mileage “sweet spots”. Also known as "spot measuring", it will also make it so you can compare your mileage with other people, and have the comparison mean something.
Here’s how to do it –
Buy a little spiral notebook. Keep it in your driver door pocket with a pen. Any time you can drive a straight, flat, constant-speed stretch of roadway, you should use that pavement as your personal mileage laboratory. Start by getting up to the desired test speed, engage your cruise control, then reset your onboard MPG accumulator. Keep your eyes on the road, but occasionally check the display. It will either climb or descend right after you reset it, but it will eventually stabilize (as long as your vehicle and engine speeds remain unchanged). Once it stabilizes, make a notation in your log book with the following data (only when stopped please):
- Date
- Speed (MPH)
- Revs (RPM)
- Indicated MPG (stabilized)
- Load (fuel level, pax, Etc.)
- A/C on or off
- Windows up or down
- Atmospheric conditions (temp, humidity, wind)
Note: to make this more organized, you may want to create a spreadsheet printout (Excel file) which has those labels as column headings, to make the recording of data easier and more organized.
Once you’ve made your test data notation, try to make a similar (repeat) run under the same conditions (on the same stretch of road) but in the opposite direction. If you get a different MPG reading, then average the two readings to get the “spot MPG reading” for that speed.
What you want to do is begin to collect spot readings of a broad range of vehicle speeds (under the same general conditions). Something like the following list of speeds: 36, 38, 40, 42, 44, 46, 48, 50, 52, 54, 56, 58, 60, 62, 64, 66, 68, 70, 72, 74, 76. Once you have those, you will very quickly see what your around town “sweet spot” and highway “sweet spot” are. Those are what your regular cruise speeds should be (city and highway) to get maximum fuel mileage.
ACCELERATION: This is the big mileage killer. It is also the reason you want to NOT include it as part of your spot mileage tests (that is why you will reset the display once you are at your test speed). My truck weighs about 8,000 pounds. Newton’s first law of motion (inertia) has a huge part to play in the life of an 8,000 pound truck. You’re going to have to expend energy to get that mass moving. Newton’s second law (acceleration) dictates how much energy you will need to expend, and how much MORE energy will be expended to get that mass moving QUICKLY.
HINT: Your turbo boost gauge is actually an energy meter. Stomp on the pedal, and the 350 (stated) horses will get that 8,000 pounds up to highway speed pretty quickly. It will also require a very large amount of potential energy (Diesel fuel) to go though a very rapid and massive energy conversion to lots of kinetic energy (heat) to make that happen. That’s measured many ways but one of them is inverse MPG (more energy expended over a constant distance results in less MPG). Your boost gauge is trying to tell you something (you knew it must be there for some useful reason). Now, you can get that same 8000 pounds up to highway speed with probably well under 100 HP if you just take your time. Much more efficient energy conversion and utilization will occur, and the result will be pronounced improvement in fuel mileage.
Why is this important (for other than the obvious reasons)? Because from a scientific measurement standpoint, your foot working an accelerator pedal is impossible to exactly repeat each time you accelerate. Also, the number of standing starts you have to make per trip (whether you’re doing 40 Lbs. [of boost] "pedal mashes", or you take a full minute to get to 60 MPH, never exceeding 5 PSI ) will NEVER be consistent. In addition, the number and degree of normal speed changes (other than to or from a stop) during a trip will NEVER be the same. This is why you have to take acceleration and deceleration completely out of your mileage calculations.
Yes, yes, yes, I know that will then not tell you what your “real world” mileage is, but you can use your calculated averages for that. The point here is to determine what your truck is actually doing (fuel mileage wise) across a broad range of speeds under fairly controlled conditions. All the differing starts and stops and speeding up and slowing down and changes in fuel load will completely cloud your efforts to generate useful mileage data. Once you have this data, you can VERY QUICKLY determine if mods or additives (or anything else) has made an immediate change in mileage, and what speeds the change is most pronounced. Just repeat your spot logging tests after the mod is installed. Also, you can then compare your mileage to other folks with the same truck (at the same speed and similar conditions) and actually be doing an apples-to-apples comparison
Trying to accurately track your mileage by any other method will cause you to tear your hair out because of the fact that there are so many variables outside your control if you are just averaging, or if you don’t completely exclude acceleration/deceleration from your measurements.
AFTERMARKET FUEL METERS: If you want to measure performance parameters with more precision, I highly recommend installing a Scan-Gauge. Just so you know that I don’t make any money off them, Google the term Scan Gauge to see what’s out there.
HYPERMILING: I’ll talk about what Hypermiling is and how to do it in a later post in this thread.
BTW – Can any of you experienced Super Duty guys tell me what the whistling sound is that I hear between 55 and 75 MPH? It seems to be coming from the area of the Sirius antenna over the driver’s position, and is more pronounced when there are cross winds. Thanks for any help (I’ll post this question on the broader forum also).
Good luck folks. Hope my suggestions prove to be helpful in your quest for better mileage. That was the whole reason for my post. I’m not into arguing on the internet, so if you have an opposing opinion, please just post it (that’s the way science works), but try to resist making it personal (that’s NOT the way science works). Thanks.
C. Palmer
Chairperson: National Hypermiling Safety Foundation
Member: Society of Automotive Engineers
Member: Engineering Society of Detroit
What I’m a little more experienced with is the art and science of maximizing fuel mileage. I am an SAE engineer and am the founder and chairman of the National Hypermiling Safety Foundation, so I think I may have something (hopefully useful) to offer to the discussion.
I have 2K miles on my brand new, very first Super Duty (’08 F-250, 6.4 TD, crew cab, auto, 4X4, 18” wheels, A/T tires, 3.55 axle, Sunoco ULSHDF, no additives, tonneau, original March 2008 factory ECU firmware).
Here’s the part where you’re all going to jump on me, but hear me out (please remember, I’m writing this post for your benefit, not mine).
According to my onboard (stock Ford) fuel flow computer/accumulator, I drove a 2 mile stretch of nearly-perfectly flat (45 MPH posted speed) south Florida pavement today (with the weight of about 26 gallons of fuel on board) and consumed fuel at a rate 23.0 MPG.
It’s not the (apparently) high MPG number that’s important (nor am I bragging about it), it’s the fact that the test was done in a moderately scientific way (which is the only way any of you should be measuring your mileage). In short, I reset the MPG accumulator once I had attained the set 45 MPH test speed (with cruise control engaged), and read the final MPG reading once it stabilized for a minimum of 30 seconds (and before altering the speed in any way). I then repeated the same stretch of road going in the opposite direction with the same measurement method, and got the same result.
Okay, this is going to be a long post, so go get your beer, go to the bathroom, walk the dog . . . I’ll wait till you get back.
Here’s what I’m talking about –
You’ve got to be scientific with your mileage measurements. You’ve got to exclude as many of the variables that are outside your control, as you possibly can. Those variables will wreak havoc with the usefulness of your measurements.
A FEW WORDS ABOUT AVERAGES: Averages are only useful if you look at them over very long periods of time, or over a very large number of samplings. When you fill up your tank, drive, then fill it again and hand compute your mileage, all you have is an average. That average is only of scientific value if you drive EXACTLY the same trip profile between every single fill-up. That means the exact same route, speeds, number of stops, driving style, atmospheric conditions, towing situation, song on the radio [just kidding] Etc. Those are all variables which invariably change every time we drive. As such, those changes in variables will cause your computed averages to vary constantly.
That doesn’t mean that those averages aren’t useful. Log those averages somewhere, and maybe after several months or years of doing that, you will be able to plot those averages on a curve over time and see some trends which you can attribute to long-term trackable factors (i.e. change in age of truck, change in age of driver , where you may have lived during the life of the truck, improvements to traffic systems in your region over time, mods, changes in your lifestyle over time, changes in your work situation over time, Etc.). Those are the only things that tracking changes in average fuel mileage can really tell you about . . . long-term trends and changes.
SPOT LOGGING: No, that’s not what your dog does in the backyard. It’s actually the only way to accurately measure (a) the actual mileage situation with your truck, and (b) help you find your truck’s mileage “sweet spots”. Also known as "spot measuring", it will also make it so you can compare your mileage with other people, and have the comparison mean something.
Here’s how to do it –
Buy a little spiral notebook. Keep it in your driver door pocket with a pen. Any time you can drive a straight, flat, constant-speed stretch of roadway, you should use that pavement as your personal mileage laboratory. Start by getting up to the desired test speed, engage your cruise control, then reset your onboard MPG accumulator. Keep your eyes on the road, but occasionally check the display. It will either climb or descend right after you reset it, but it will eventually stabilize (as long as your vehicle and engine speeds remain unchanged). Once it stabilizes, make a notation in your log book with the following data (only when stopped please):
- Date
- Speed (MPH)
- Revs (RPM)
- Indicated MPG (stabilized)
- Load (fuel level, pax, Etc.)
- A/C on or off
- Windows up or down
- Atmospheric conditions (temp, humidity, wind)
Note: to make this more organized, you may want to create a spreadsheet printout (Excel file) which has those labels as column headings, to make the recording of data easier and more organized.
Once you’ve made your test data notation, try to make a similar (repeat) run under the same conditions (on the same stretch of road) but in the opposite direction. If you get a different MPG reading, then average the two readings to get the “spot MPG reading” for that speed.
What you want to do is begin to collect spot readings of a broad range of vehicle speeds (under the same general conditions). Something like the following list of speeds: 36, 38, 40, 42, 44, 46, 48, 50, 52, 54, 56, 58, 60, 62, 64, 66, 68, 70, 72, 74, 76. Once you have those, you will very quickly see what your around town “sweet spot” and highway “sweet spot” are. Those are what your regular cruise speeds should be (city and highway) to get maximum fuel mileage.
ACCELERATION: This is the big mileage killer. It is also the reason you want to NOT include it as part of your spot mileage tests (that is why you will reset the display once you are at your test speed). My truck weighs about 8,000 pounds. Newton’s first law of motion (inertia) has a huge part to play in the life of an 8,000 pound truck. You’re going to have to expend energy to get that mass moving. Newton’s second law (acceleration) dictates how much energy you will need to expend, and how much MORE energy will be expended to get that mass moving QUICKLY.
HINT: Your turbo boost gauge is actually an energy meter. Stomp on the pedal, and the 350 (stated) horses will get that 8,000 pounds up to highway speed pretty quickly. It will also require a very large amount of potential energy (Diesel fuel) to go though a very rapid and massive energy conversion to lots of kinetic energy (heat) to make that happen. That’s measured many ways but one of them is inverse MPG (more energy expended over a constant distance results in less MPG). Your boost gauge is trying to tell you something (you knew it must be there for some useful reason). Now, you can get that same 8000 pounds up to highway speed with probably well under 100 HP if you just take your time. Much more efficient energy conversion and utilization will occur, and the result will be pronounced improvement in fuel mileage.
Why is this important (for other than the obvious reasons)? Because from a scientific measurement standpoint, your foot working an accelerator pedal is impossible to exactly repeat each time you accelerate. Also, the number of standing starts you have to make per trip (whether you’re doing 40 Lbs. [of boost] "pedal mashes", or you take a full minute to get to 60 MPH, never exceeding 5 PSI ) will NEVER be consistent. In addition, the number and degree of normal speed changes (other than to or from a stop) during a trip will NEVER be the same. This is why you have to take acceleration and deceleration completely out of your mileage calculations.
Yes, yes, yes, I know that will then not tell you what your “real world” mileage is, but you can use your calculated averages for that. The point here is to determine what your truck is actually doing (fuel mileage wise) across a broad range of speeds under fairly controlled conditions. All the differing starts and stops and speeding up and slowing down and changes in fuel load will completely cloud your efforts to generate useful mileage data. Once you have this data, you can VERY QUICKLY determine if mods or additives (or anything else) has made an immediate change in mileage, and what speeds the change is most pronounced. Just repeat your spot logging tests after the mod is installed. Also, you can then compare your mileage to other folks with the same truck (at the same speed and similar conditions) and actually be doing an apples-to-apples comparison
Trying to accurately track your mileage by any other method will cause you to tear your hair out because of the fact that there are so many variables outside your control if you are just averaging, or if you don’t completely exclude acceleration/deceleration from your measurements.
AFTERMARKET FUEL METERS: If you want to measure performance parameters with more precision, I highly recommend installing a Scan-Gauge. Just so you know that I don’t make any money off them, Google the term Scan Gauge to see what’s out there.
HYPERMILING: I’ll talk about what Hypermiling is and how to do it in a later post in this thread.
BTW – Can any of you experienced Super Duty guys tell me what the whistling sound is that I hear between 55 and 75 MPH? It seems to be coming from the area of the Sirius antenna over the driver’s position, and is more pronounced when there are cross winds. Thanks for any help (I’ll post this question on the broader forum also).
Good luck folks. Hope my suggestions prove to be helpful in your quest for better mileage. That was the whole reason for my post. I’m not into arguing on the internet, so if you have an opposing opinion, please just post it (that’s the way science works), but try to resist making it personal (that’s NOT the way science works). Thanks.
C. Palmer
Chairperson: National Hypermiling Safety Foundation
Member: Society of Automotive Engineers
Member: Engineering Society of Detroit
Last edited by cp101; 04-28-2009 at 08:20 PM. Reason: Typo correction
#34
04-28-2009, 08:43 PM
Okay, okay, sorry for the head aches. Here's the advice in a nut shell:
Measure your mileage by engaging cruise control and then resetting your mileage meter. Once the number stabillizes, write it down along with the speed you were travelling. Do this on flat stretches of road without changing the speed of your truck. Do this for a bunch of different speeds. Whatever speeds generate the best MPG are your "sweet spots". Drive those speeds . . . save lots of money.
Wow . . . I don't think I've ever put my ideas into a single paragraph before. I should try that when I do public cpeaking (probably more people will stay awake). Hey thanks guys!
With brevity,
C. Palmer
Measure your mileage by engaging cruise control and then resetting your mileage meter. Once the number stabillizes, write it down along with the speed you were travelling. Do this on flat stretches of road without changing the speed of your truck. Do this for a bunch of different speeds. Whatever speeds generate the best MPG are your "sweet spots". Drive those speeds . . . save lots of money.
Wow . . . I don't think I've ever put my ideas into a single paragraph before. I should try that when I do public cpeaking (probably more people will stay awake). Hey thanks guys!
With brevity,
C. Palmer
#37
04-28-2009, 09:25 PM
One of the best descriptions of Hypermiling can be found here:
http://www.cleanmpg.com/forums/showthread.php?t=1510
http://www.cleanmpg.com/forums/showthread.php?t=1510
#38
04-28-2009, 09:33 PM
New User
Join Date: Nov 2008
Location: Like muh 5 acres
Posts: 24
Likes: 0
Received 0 Likes
on
0 Posts
Sounds good to me.
I used to get a real good average MPG coming down the hill from Tahoe..
==========
On the whistling sound, open your rear slider a bit and see if that doesn't help you identify it, it did for me.
I have some moveable track racks on my truck, aNd the way I had it set up,
it would make a ridiculously annoying whistle over 35 MPH.
====================
I used to get a real good average MPG coming down the hill from Tahoe..
==========
On the whistling sound, open your rear slider a bit and see if that doesn't help you identify it, it did for me.
I have some moveable track racks on my truck, aNd the way I had it set up,
it would make a ridiculously annoying whistle over 35 MPH.
====================
#40
04-29-2009, 07:18 PM
Hypermiling is the art of being in the way of everyone behind you so that you may maximise fuel economy by using the least amount of throttle movement possible and planning your stops so that you can coast to the last second before applying brakes and perhaps you'll get lucky and the traffic ahead will move so that you don't have to stop thus maintaining monentum and not having to use extra energy to regain lost momentum. In short, it's the art of p###ing people off behind you and making oneself vulnerable to being struck from behind by another vehicle whose driver may not even have a clue what you're doing because they were multitasking while driving.
#41
04-29-2009, 08:32 PM
Hence why we formed the Hypermiling Safety Foundation. To develop safer ways of saving fuel. Hypermiling in its extreme forms can pose certain safety issues. The safest (and most effective) way to hypermile is to figure out (before starting the engine) if that trip really is necessary, and if it is, then how to organize the trip to maximize efficient use of the vehicle. Doing the speed limit (or 5 MPH under) in the right lane helps too, without decreasing road safety.
#42
04-30-2009, 01:00 PM
Lead Driver
I use a safe form of hypermiling, it's call anticipatory driving. I don't treat every block between stoplights as a drag strip and if the light turns yellow I'll coast to the light in hopes that my wheels don't stop before I get there. I won't idle at 7mph to avoid the light. I also don't run stop signs or lights to save a few drops of fuel. Additionally, I didn't buy my Super Duty because of it's fuel mileage. It's a big, heavy truck and it is going to act like it and suck fuel like I'm trying to move 4 tons of steel down the road. I try to conserve where I can and drive efficiently (smartly), i.e. set the cruise at 65mph (my truck loves to cruise at 1800rpm, good balance of power/economy), but I think the extremes that some of the hypermilers go to is not as efficient as they might think (I'd rather burn a little extra fuel than put my engine through the stress of shutting it down and starting it up at every red light), not to mention causing a hazard on the roadway.
Sorry for the rant, just my .02
Sorry for the rant, just my .02
#44
05-02-2009, 10:13 AM
Senior User
Join Date: May 2003
Location: Frederick MD & missing AK
Posts: 286
Likes: 0
Received 0 Likes
on
0 Posts
The method you described to measure fuel efficiency sounds like a great way to "pad" your "hypermiler" numbers. It is useless to most folks because those variable that you try to delete are things we deal with everyday. Yeah, you make for a fine scientific experiment with as close to laboratory conditions as possible, but it is impractical for most, if not all, drivers.
I would rather know what my truck is getting while I am driving it under normal, everyday conditions, than know what it is capable of getting under "perfect" conditions.
BTW, I have been to a couple hypermiler websites to try and gleen a tip or two that might help my fuel consumption. Most of those forums are just a bunch of hybrid drivers who brag about getting rediculous mpg's while performing unsafe driving to get them. It is an ego thing, just like HP and TQ is here.
I would rather know what my truck is getting while I am driving it under normal, everyday conditions, than know what it is capable of getting under "perfect" conditions.
BTW, I have been to a couple hypermiler websites to try and gleen a tip or two that might help my fuel consumption. Most of those forums are just a bunch of hybrid drivers who brag about getting rediculous mpg's while performing unsafe driving to get them. It is an ego thing, just like HP and TQ is here.
#45
05-02-2009, 12:03 PM
Senior User
Join Date: Mar 2009
Location: Western Mass
Posts: 150
Likes: 0
Received 0 Likes
on
0 Posts
It's the emmissions stuff that's killing fuel mileage. I've read on other forums that elimination of the DPF and reprogramming to eliminate regeneration on the 6.4L trucks is good for an additional 4 mpg. Same for Dodge and Chevy. The tree huggers and EPA have killed the diesel fuel economy for now.