Raising Gas Mileage on a 2003

[Richard L]

Dean,

I have no axe to grind with you, nor do I feel that your ProScan formula is inaccurate, or that it is not calculating correctly. My only concern is that it is getting information about the distance traveled from the factory VSS unit which are known to be in accurate by as much as 5%. I never said your VSS is off by 5%, but if you can't or won't calibrate your ProScan you will never know how far off your VSS is or how far off your MPG calculations are..

What I'm going to attempt to do here is gather some highway and commute mpg data, to establish a baseline, and then perform some mods to see if there is an improvement.

That will only work if you have an accurate baseline, and it will take a lot more than a single 200 miles test to eliminate all the possible traffic, road, terrain, wind, and weather variables that effect your mileage.

So, you have now found yourself in the position of having to argue that the unit is not repeatable in it's method of measurement. I happily await your response in this regard for it is based on a well accepted formula and the consistency of the speed and mass air flow sensors.

I never said your test were not repeatable, but if you use the same inaccurate input for your MPG calculations your results will always be repeatable, but wrong!. Your statements have shown me that you are not being very precise or scientific in your MPG quest. I am not convinced that your numbers and claims are very accurate, and some statemests you made show me that you are not even trying to be accurate, but appear to want to squeeze every fraction of a MPG from every drop of gas. You can do that if you are so inaccurate in your measurments.

The fact of the matter is that my tires are well within 1% of the diameter of the stock tires. I also highly doubt the vehicle speed sensor is off by 5%. AND: n early October I drove up to Lake Wanpaupak on a 252 mile round trip. Unfortunately I did not have Proscan running on this trip. But I do know that the fuel gauge still read over half a tank left over when I got back home.

First, I have asked you twice and you still have not said if your ProScan can be calibrated for VSS inaccuraciies? If it cannot be calibrated, or if you have never calibrated it, then you don't really know your true MPG. If you calibrated your ProScan to the VSS, then tire size would not matter, but if not, then your statment that your tire size is within 1%, can become much bigger error when calculating MPG.



I also don't think anyone who uses the Fuel gauge to estimate MPG is very serious about accuracy and will just round off numbers or use other guess-timations and excuses to claim they are getting better mileage. The fuel gauge is known to be far more inaccurate than the VSS and should never be used to calculate MPG...It's not even good for guess-timations of MPG !!!



I used to drive over 100 miles in my Sport Trac before the fuel gauge would even fall below a full tank??? Does that mean I drove 100 miles without using any gasoline? NO! It just means that the fuel gauge is a piss-poor tool for calculating gas mileage !



No VSS from the factory is 100% accurate...so I cannot accept that your GPS and your factory Speedometer are giving the exact same reading. VSS are purposely made to give a slightly higher speed/odometer reading for several reasons. The car maker does not want to be sued for someone getting a ticket because their speedometer was reading too low.



That also makes the Odometer read more mileage than the vehicle has actually traveled...That's to the Manufacturers benefit in Warranty issues...a 36K mile warranty may expire on the odemeter, when the vehicle has really only traveled 35K miles or less !



I don't really care what your MPG is, and because I cannot witness or verify the accuracy of your questionable test procedures especially when they are much higher than normal, I cannot confidently accept anything you say regarding your gas mileage...good, bad or otherwise?



The reason I am calling you out on this subject is because your MPG claims will make some other Sport Trac owners assume that they can get the same mileage as you claim to be getting...when your MPG figures are based on too many inaccuracies to be trusted



I have problems with people who claim to get high gas mileage and then explain their calculations based on their fuel gauge or unfounded or unreliable mentods as you just did?? They defend the accuracy of their testing and calculations when in reality they have no way of knowing exactly how much gas is actually in the tank or how much gas they actually used during the test...That's exactly what you are doing.



...Rich

 

[Dean Hedin]

Wow, such doubt. That's OK, it's good to doubt. Not enough people doubt these days... young people in particular.



In order to appease Richard (and others) I have devised a little experiment.



I'm going to drive to Cabela's in Hamburg, PA sometime in the next few days for some Holiday shopping. I haven't been up there in a few years.



It is about 70-75 miles each way. Probably 145 miles round trip.

The majority of the trip is on the Pennsylvania Turnpike and up the North East extension.



The trip will start at gas station near the Willow Grove PA Turnpike entrance.

I am going to top off the tank and note the pump that I have used. I will set the gas nozzle at it's lowest fill setting and let it "auto click/stop" ONCE and make no attempt to fill any additional fuel.



I will then zero the Sport Trac trip odometer, and reset Proscan.



I will then proceed to drive to Cabela's. Once I get to Cabela's I will record

the Proscan MPG reading for the outward trip.



I will then shut everything down and go shop at Cabela's.



When I leave Cabela's I will reset Proscan and return back to the turnpike

the way I came and back to the original gas station I started from.



I will then go to the same pump I filled with before. I will then top off the

tank in similar fashion as I did at the start of the journey. I will also record the MPG data measured by Proscan for the return trip.



I will record the gallons indicated on the pump to top off and calculate the MPG using the

Sport Trac's odometer miles elapsed (or even from the GPS if so desired).



We will then compare this with the MPG data acquired by Proscan.



Now...

I am not saying that I will get 25.5 mpg on this particular trip. But I might!



I will do everything I can to get the best MPG through driving technique, but that is not the point of this experiment.



The point of this experiment is to see how well Proscan jives with reality.



I'm sorry I can't offer anything better Rich. This is the best I can do. I'm not forking up the expense to drive across country to prove things out to you.



None the less I willing to concede that it is possible that the Proscan software is in error by a fixed offset. Maybe it is reading high. We may discover that this is the case after this experiment. But it might be spot on.



I still hold that Proscan (and other OBD2 solutions) achieve very repeatable results by the means of utilizing the mass air flow and speed sensors of the vehicle and by a well accepted technique to determine the MPG. It is sufficient to allow me to perform economy modifications going forward and note the improvements of those modifications. We may argue over the magnitudes of the values, but not the deltas.



Is this sufficient for you Rich? Probably not, but it's good enough for me (and perhaps others) and I look forward to the results.



Need I remind you that I am making all the effort here. It is in my own interest here to do these things.



I wish to know if Mobil 1's claims regarding 0-30W Economy synthetic oil are valid. If I can't "see" a difference with Proscan with a long highway trip then it probably is not worth it.



What experiments, pray tell, does Richard have planned for us in the forthcoming days regarding these matters?



Take it or leave it. All disclaimers apply. And I don't care if you go screaming all through this thread for the next few months as I collect my data. But if you want to make a difference, take some measurements of your own, by whatever means you wish, and prove me wrong - or right?



That's the beauty of the scientific method. Are you prepared to muscle up and validate or invalidate my results by experiment?



This is gonna be fun. I'm gonna get YOU to start disproving my experiments in increasing MPG. Ain't that great?

 

[Richard L]

Dean,

You just don't get it do you???. All I am saying is that if you are using the factory Speedometer/Odometer VSS readings to measure the distance travel, you are most likely going to get an inaccurately high Average MPG.



Also pumps don't all shut off at the same level of fuel so you will never get an accurate measurement of a full tank by simply assuming the pump will always shut off when the tank contains the same amount of fuel. The only way to know is to fill the tank to the pump shut off, and then slowly fill the tank barely a trickle at a time until you can see the gas in the filler pipe just above the nozzle restrictor plate. Now you know exactly what level you need to fill your tank to at the end of your trip to get an accurate quantity of fuel used....and don't round off the tenths or hundredths of a gallon that the pump shows.



For most people that amount of accuracy is more than enough, but if you are truly on a QUEST, you want reliable accurate data. You are wasting a lot of time and trouble for another inaccurate reading simply because you are not factoring in the speedometer/odometer error. BTW, you still have not said anything about calibrating the ProScan???



Until you know the exact amount of VSS error, or you can calibrate the ProScan, your MPG readings are not any more accurate than a simple guess-timation.



I will never except your MPG claims until you can prove that you have run an accurate test and not for just 145 or 200 miles. Remember: The smaller the sample, the bigger the error !



Every time you post here, you convince me more and more that you do not know how to do a really accurate MPG test because you make too many assumptions that your VSS is accurate, the fuel gauges is accurate, and because your ProScan uses a proven formula that somehow it will know that your VSS is sending it inaccurate information?



If VSS were accurate, UltraGauge, ScanGauge and others would not provide for calibrating for VSS errors.



...Rich

 

[Richard L]

 

[Dean Hedin]

Oh I see. I'm going on a trip that will potentially consume more than 6 gallons of gas and the pump is going to be SO FAR OFF the second time I go to fill it? Please.



Tell you what, I'm going to fill it to the point that it just gets to the top of the fill neck (in both cases) Will that satisfy you then? Nope...probably not. But that is what I am going to do. I don't want there to be any doubt on this in my own mind. I am equally interested as you are to get to the truth.



In the end Rich, it doesn't matter to me if Proscan is off by a fixed amount. Fine, you will be vindicated.



The point is that it's a repeatable method of measuring the fuel economy. If I make improvements I will see an increase using this method of measure. That is all that matters.



It's not like my vss is going to be 10% off this week and 5% next week.. This is the part that you don't seem to want to acknowledge.

 

[Richard L]

Dean,

Oh I see. I'm going on a trip that will potentially consume more than 6 gallons of gas and the pump is going to be SO FAR OFF the second time I go to fill it? Please.

Yes! That's exactly what I mean !!! "Small samples cause Big errors"...That's what I am trying to get you to understand! Those seemingly small inaccuracies that you dismiss as insignificant, in a small test (100-200 miles) can induce huge errors in your results. If you were to conduct a test several thousand miles and 4-5 tanks of gas or more, then you would get a much more accurate fuel mileage figure because all those small inaccuracies would then be rather insignificant. That's why I and others are saying that a short trip with so many inaccuracies do not give you and accurate Average MPG



My UltraGauge can show that sometimes I can get 150+ miles per gallon, but only for a few seconds or a few hundred feet when I take my foot off the gas going about 70 MPH. So technically I could say that my vehicle gets as much as 150 MPG??? But I don't, because I know I am taking a very small sample reading.



A one tenth of a mile distance error, or a tenth of a gallon error when calculating MPG when you have only driven 10 miles makes a huge impact your MPG calculation. But that same tenth of a mile or tenth of a gallon error on a test of 1000+ miles is very small and insignificant.



So let me clarify: I don't care what mileage you get on your Sport Trac, So don't do this to impress me or try to convince me of anything. You are free to conduct your mileage test any way that makes you happy. However, when you start making claims here that your gas mileage figures are well above average, and you only conducted a 100 mile test, I begin to question the accuracy of your tests in such a small sample...(It's not just you, I have called others out on their MPG claims and testing methods as well) That's when it is usually revealed that they are not getting accurate fuel usage numbers because they assume that filling until the pump shuts off is accurate, or they are using the fuel gauge to calculate (guess?) the fuel used and assuming their Odometer is 100% accurate???



Because "Small samples cause Big Errors" especially in obtaining an Average MPG, it is very important to be very accurate in all your measurements when conducting those short 100-200 mile tests. You must have accurate readings of exactly how much gas you used, and exactly how many miles you traveled. If either of those numbers are off by even a little bit on a short test you will get inaccurate calculations



If you cannot calibrate your ProScan, for an accurate "Driven Distance"...and you cannot keep your ProScan/laptop connected all the time like I can with my UltraGauge, Then don't run those short 100-200 mile tests. Drive the vehicle for a few months and keep track of the fuel used and miles driven.....When you have driven about 2000 miles, simply calculate your mileage manually from those figures and you will have a much more accurate and realistic sample of your Average MPG, even with the inaccurate VSS Speedometer/Odometer reading.



...Rich

 

[Dean Hedin]

Rich, if I fill it to the neck at the start of the trip, and I fill it to the neck at the end of the trip, it will be a sufficiently accurate measure of fuel used.



I'm not interested in driving my car in mixed city/highway conditions over the course of a few months to determine the overall MPG.



This test is strictly a highway mileage test to see how well Proscan jives with reality.



If I drive 140 miles and when I return to the station and it takes 6 gallons to fill it back up to the neck then I did 23.3 miles to the gallon. If Proscan is in agreement with this then I will be satisfied with it's accuracy. We can double check the actual mileage traveled with GPS or with google maps if you have doubts regarding the Sport trac's odometer reading.



When I say "fill it up to the neck" I mean I will physically look into fill hole an use a visual reference point to make sure I fill to the same point each time.



This is a simple test and is sufficiently accurate to determine if Proscan is "WAY OFF" like you presently believe it is.

 

[Richard L]

Dean,

I never said your ProScan is WAY OFF? Your ProScan will probably agree closely with your manual calculations because you are both using the uncorrected distance traveled from the VSS.

If you conducted the test over 2000 miles or so, you will get a different MPG calculation because the effect of the VSS error has been minimized by the longer distance traveled. Larger sample means smaller errors.



That's why I got the UltraGauge because it can calibrate for Speedometer/Odometer error as well as fuel level (some vehicles use the fuel level sensor to determine fuel used, miles to empty, etc) My Hyundai does, but my Mercedes does not.



Oddly enough, when I fill up my Hyundai, it says I will be empty in about 380 miles, however my UltraGauge says it will go over 450 miles. As I drive and use more fuel, the Hyundai gauge starts to extend the mileage until it agrees with the 450+ miles that is displayed on the UltraGauge...:grin: My Hyundai speedometer reads 2.5-3 MPH too high at all speeds above 30 MPH...ie: When the speedometer says I'm going 50, I am really only going about 47 MPH. If I ran a mileage test of 50 miles, I would have only traveled about 47 miles and that can create a significant error in in the MPG calculation.



I recently went on a 2400 mile trip to Ohio and back and the Hyundai calculated that I was getting 31.2 MPG with an average speed of 70 MPH, however my UltraGauge was calibrated for the Speedometer error and calculated a more accurate 29.7 MPG with an average speed of 68 MPH. My Hyundai is estimated to get 30 MPG Hwy miles, so I am confident that 29.7 is pretty accurate considering that I don't really drive in any particular way to save gas.



...Rich

 

[Dean Hedin]

The Cabelas Experiment...



Purpose: To determine if there is any offset error in OBD2 softeware

MPG determination.



Everything went pretty much as planned.



It got cold around here so before I left I checked the air in the

tires and set them to 38 psi. Glad I did as they were about 4 psi low.



The temperature was about 37 degrees when I left at around 10 am.



I had a separate GPS to track the mileage. This GPS also allows me to

download the track of the journey, which I have done.



Traffic was light, I tried to stay around 60 mph. The nice thing about

this trip is that it is virtually ALL highway. There was no mingling in

traffic or stop lights. Just the pauses at the toll booths.



The GPS indicated 56.2mph average speed going to and 57.2mph on the way

back.



The mileage data is as follows:



Proscan:

71.9 miles to Cabelas

70.68 miles back

142.88 total



Sport Trac Odometer:

71.82 miles to

71.6 miles back

143.42 total



GPS Tracking

71.82 miles to

72.34 miles back

144.16 total



Google maps:

71.6 miles to

72.4 miles back

144.0 total



I think from the above data we can safely say that there is no significantly

large VSS error on my Trac.



Proscan MPG readings:

To Cabelas 22.61 MPG 3.13 gallons used

Back 22.96 MPG 3.10 gallons used



To/from distances are pretty close, so we can average these and get:

22.785 MPG overall on the trip.



BTW, this trip involved some elevation changes. It's sort of an ascent to Cabelas

and a descent back home. This is reflected in the to/from mpg values.



But how much gas was really used? When I got back to the gas station

I filled it back up in the same manner as when I departed. To keep it

"fair" I did not look at the pump while topping off until I was finished.



When I turned around and looked , the pump indicated 6.68 gallons.



Using this fuel usage and the GPS mileage (which I trust the most) I get:

144.16/6.68 gallons = 21.58 MPG



It seems that Proscan is reading 1.2 mpg too high. Surprise surprise!



But why?



I think I know why. Programs like Proscan (and other ODB program/readers) are

looking at the mass air flow sensor and using the familiar 14.7 to 1

stoichiometric air/fuel ratio to determine the fuel burnt. It's a very

sensible and accurate approach. Especially in the case of steady state highway driving.



There is just one problem. I'm not burning gasoline.

Remember what the pump says? "This gasoline may contain up to 10% ethanol".



A cursory internet search indicated that there is about a 4-5% loss when

running 10% ethanol. That does not account for all, but I believe it

accounts for a large part of the discrepancy.



As I have stated previously I'm not to worried about this discrepancy. It is a simple

scaled offset.



I am confident I could do this trip again and get results very much the same.

I'm calling this is a "baseline winter highway trip".



Sometime in the next few weeks I'm going to do this same trip again, after

I've changed the engine oil to Mobil 0-30W with a 1% Molybdenum di-sulfide

additive. I expect a 2-3% increase by doing this. I think that kind of improvement

will show up on a trip like this. I'll try to pick a day with similar temperature and traffic conditions and we will see what happens.

 

[Richard L]

Dean,

Good job. It sounds like you did an accurate test and the results show what most people would expect to get from a 2003, Gen-1 Sport Trac which is right about the same MPG I got with my 2001 and 2003 Sport Tracs....but not the inaccurate 25.5 MPG you originally posted



I also suspected that your ProScan and Sport Trac Odometer would get close to the same mileage because they are both using the VSS for Speedometer and Odometer readings, but I am surprised that your VSS is that accurate and so close to the actual mileage...Most are off by a lot more. My Hyundai Speedometer/odometer is off by nearly one mile in a measured 10 miles? Also, the Hyundai's MPG trip computer was very close to my UltraGauge reading over a combined 2400 mile trip....So, perhaps the Speedometer/odometer digital gages are inaccurate, but the VSS is closer to correct?



...Rich

 

[Dean Hedin]

Well, I told you my tires measured the same diameter as stock.



But I must state that earlier this year I did do a trip, where Proscan indicated 25.5 MPG

Knowing what I know now that figure was about 1.2 MPG higher than actual, the result is 24.3 MPG which is still impressive, but you probably still don't believe. That trip was on a warm day, and on flatter terrain.

 

[Richard L]

Dean,

Your previous tests were not conducted as accurately as this last test. I never said your tires were not the same diameter as stock, but you don't know that because you never measured your old tires? You just assumed they were the same diameter because they were the same size. but a quick check at TireRack.com will show that different manufacturers and different tires styles will have different diameters even though they are the same tire size.



Also, when you measured your tires you said they were "About 29 inches"... That just tells me that you are very imprecise in your measurements and that your previously claimed MPG figures where also inaccurate as well.



It appears that now you have a reasonably accurate MPG figure and it is in the same range that most people could expect to get. You cannot take your highly inaccurate earlier claim of 25.5 MPG and just assume it was 1.2 MPG too high and now claim that you get 24.3 MPG now. You are letting your inaccuracies in the early tests creep in to contaminate your latest most accurate test.



That's where I have a problem with your logic...you make too many assumptions and too many illogical conclusions that have not been accurately proven and you don't really seem to understand how one or two inputs don't provide a very accurate "Average"



Remember, I said that "Small samples cause big errors"....This is very true, especially when calculating Averages. All of your tests are based on short trips of 200 miles or less which magnifies any inaccuracies you your testing. You need to go on a trip of 1500 or 2000 miles or drive the vehicle for a month or two, that requires 4-5 full tanks of gas, and that will give you a much truer "Average" MPG figure. That's what average means, and 144 miles and 6.68 gallons of gas is really not an Average when you only have one or two values to use in that Average.



I also have to question you last test where you state that your Sport Trac odometer registered your trip as 71.82 Miles to Cabela's. I owned two Sport Tracs, a 2001, and a 2003 and neither had an Odometer that would display 100ths of a mile???? That now makes me suspicious of what other assumptions and inaccuracies have crept into your calculations.



Every time you post to support your MPG claims you continue to make statements that make me wonder how logical and accurate you really are in your mileage tests? Your latest test appears to be more accurate and the results are more realistic, but then you contaminate that test by stating an odometer reading that cannot possibly be true because the Sport Trac odometer only displays tenths of a mile...not 100ths of a mile. Yes it's a very small error, but now I am suspicious of how did you got all your other mileage figures???



You can post any MPG figure you want here. I think I have shown that your mileage testing methods are highly questionable, and people here can choose to accept or reject them.



I'm done discussing this with you. I tried to help you get accurate MPG readings and you don't appear to be willing to do that?



....Rich

 

[Yardsale]

:soap:

 

[Gavin Allan]

In order to obtain accuracy, you need to log your fuel usage and mileage driven for several tank fills. I would guess at least 5-10 tanks of gasoline. Divide the total miles driven over the period by the total amount of gas used during the period. Only then will you get a MPG figure that has a level of confidence in it. The more samples you use, the more accuracy you can ascertain.



It sounds like you confirmed somewhat that your odometer is close to accurate. You cannot confirm the fuel pump accuracy easily- that is why you need to do it over time, using many fillups from a bunch of different pumps and different stations. Many fillups will help average and reduce the errors of the fuel pumps.



I am very surprised your numbers were that repeatable just by using six gallons of gas and using the pump's auto-shutoff. I suspect that was more of a fluke of good luck, rather than due to accuracy and repeatability.



This is just basic statistics and sampling theory, with some practical experience using SPC techniques in industrial processes. It would be helpful to chart the MPG of each tank on an Xbar and R chart over a long period of time so you can see patterns and non-normal variation in able to find assignable causes. Taking what you learn in consideration, you could really dial in some good fuel economy for the variables that are under your control.

 

[Dean Hedin]

Relax Rich, the 71.82 is an error while transcribing to the post. Just checked my notes, it should have been 71.2. 71.82 was the GPS value



I hate to keep discussing the tire size Vss error, water under the bridge as far as I'm concerned. But what kind of Vss error do you think 29.1" diameter vs. 29.0" will introduce? It's nothing really, It's something like 0.3% This is what I meant by "about". I just used a yard stick. It's not like I have a giant set of tire calipers. It's hard to measure tire diameter to .1" resolution with a yardstick. Even tire pressure variation will change the effective tire diameter by that amount. A quick gander at tire rack of the P235/70-16 tires shows that most are within .1" of 29".



But this neither here nor there as the data collected thus far shows that speed sensor, odometer, and GPS are within less than 1% of each other. Rich seems to find this a surprise. I do not.



I think for this course, I have measured highway MPG to a very high accuracy. I don't need to multiple tank fills or drive thousands of miles to get a more accurate result.



I am only interested in the fuel economy across this particular course. Not in general.



The distance was measured extremely accurately via GPS. I would say that the gasoline was measured to within a few fluid ounces. Knowing that in 6.6 gallons there are about 845 fluid ounces. I would have to be off by more than 8.45 fl oz to introduce even a 1% error.



I am confident that if I were to do this trip again (under similar weather and traffic conditions) I would get very similar numbers.



I am also confident that if I do an economy modification that supposedly would result in a 3-4% increase in MPG, that we would see this in the resulting data if I were to traverse this course again.



A 4% MPG increase would mean going from 21.58 to 22.44 round trip. That would be significant and noticeable.



What was discovered and was the primary purpose of this experiment was determining how far off the ODB2 software was. It looks like it is reading about 5.3 % too high. I've given my hypothesis as to why this is occurring. But I think what is interesting is this error is not attributable to a tire size or Vss calibration issue. I think that is important, because as Rich has pointed out, some OBD MPG tools have a Vss calibration factor. Even with this correction your MPG reading could still be off.



The only way to verify the MPG reading from a OBD reader is to perform an experiment like the one I've just done, drive a known distance and measure how much gas was used.



When I perform this trip again it will be interesting to see if the software will be off by this same factor again. I hope that it is the case because it may mean that I can use a simple scaling to "correct" its MPG reading.

 

[Gavin Allan]

What is interesting is that sometimes I can only "force" about a 1/2 of additional gallon of gasoline into the tank after the pump automatically clicks "off". Other times I can "force" over 3 gallons of additional gasoline into the tank after the pump automatically clicks "off".



Using the automatic pump fill shut off to try to determine gasoline consumption by the engine is insane. That is why you need to use the volume of gasoline consumed over many tank fulls of gas to get anything approaching a level of accuracy, unless you install a mass flowmeter of some sort in the fuel line.



You may also want to learn about significant decimal places in your calculations.



Your method as you described it is full of potential measurement and calculation errors. Several members here have tried to be helpful to you, but apparently you know it all already and do not want any help. That is fine, but when you start confusing other forum members about outrageous and incorrect MPG claims and faulty methodology, that is why some have tried to step in and help you. We could really not care any less what MPG you think you may be getting and how you think you arrived at it. Unless you drive that one particular route exclusively, that is not indicative of your average fuel economy. I could calculate my economy on a 5 mile decent and give you a very high number, but it is meaningless unless that is the same route and manner that everyone else drives their tracs. The attempt of the EPA rating is to simulate a "real-world" route that is reproducable and repeatable for comparison between different vehicles. The EPA method is also not totally applicable for every driver, but it is the best we have for comparing gas mileage.

Your calculations also do not consider the gasoline formulation (% ethanol, etc.) that varies from gas station to gas station, and between tanker loads delivered to each station. Give my Trac 100% gasoline (no ethenol) and I would predict a 15-20% increase in MPG over a tank with 10% +? ethanol.



Anyway, please have a happy and safe Thanksgiving.

 

[Richard L]

Thanks Gavin,

You pointed out exactly what I have been trying to get Dean to understand. MPG reading from small trips are often highly inaccurate. Regardless of how accurate you try to be, very small discrepancies in the Mileage, or gallons of gas used have the potential to create very sizable errors in calculating an Average because you only have a few data sources to use as input.



Dean,

The fact that you made one error in the mileage makes me suspicious of all your numbers. They very well be inaccurate or simply made up..



As I previously said, I don't care what your MPG is, but I do object to posting exaggerated gas mileage figures based on short trips and inaccurate measurements.



That's all I care to say on this subject !!



...Rich

 

[Dean Hedin]

Have I not made it clear that at both the start of the trip and at the end I topped up to the filler neck?



Gavin, There is no chance of an extra half gallon of fuel being added. I took the extra care of force filling it to ensure there is no error introduced like this.



And for the upteenth time, I am not trying to establish my average fuel economy. I just want to establish the economy on this particular route. So then I can re-run this course later, after doing some fuel economy mods, to see if there was an improvement.



Rich - In one post



"Good job. It sounds like you did an accurate test and the results show what most people would expect to get from a 2003, Gen-1 Sport Trac"



to another...



"The fact that you made one error in the mileage makes me suspicious of all your numbers. They very well be inaccurate or simply made up."



All because I miss-type one number from my notes to the PC? Sorry, man, I'm only human.

Rest assured the numbers are not made up, I don't waste my time typing rebuttals to contrived data I collected for entertainment purposes. I am doing this to satisfy my own curiosity and for no other reason. I am also not trying sell anything here.



This trip was my baseline, I'm going to drive it again after making some fuel economy improvements, and measure in same fashion.



I do not expect the fuel economy to drop after making the modifications. If it does then I'll question my measurement methods. If it goes up significantly then maybe we have something to argue about. In any case this is what I'm going to do. Take it or leave it.