How are you measuring MPG improvements?

[JHZR2]

I read a lot of folks on here claiming MPG improvements. Bigtime ones at that, quite often.

While I don;t deny that MPG improvements are possible, especially in dirty or neglected engines, I have to wonder how these figures are determined.

You'll need at least 5 FULL tanks before and after to determine any sort of actual difference.

An instantaneous scangauge reading, or tank before and after measurements are nearly irrelevant. I have found myself, and Im sure others are the same, driving differently after doing something 'significant' to my vehicle, like trying a new oil, etc.

I am not denying your claims, but there needs to be a level of reproducibility. No matter how much it seems so, most roadway tests are not under the same conditions. There are too many variables that could be considered.

I would suggest that if you are considering doing a treatment of any sort, and want to gauge economy improvement, run five tanks, from full to empty beforehand, and then do at least five tanks afterwards. Be sure you fill up completely (until the pump shuts off, and then maybe a couple squeezes after that) EVERY time, and drive to at least 1/4 tank, if not lower.

I think this will help us all gauge economy improvements better... perhaps we can then track them in a database, by average economy percentage improvement or similar metric. It would be very intertesting.

Thanks,

JMH

 

[Ugly3]

Bravo!

 

[kenw]

What??? actual, real and reproducible DATA??

what fun it that?

a side note: our 93 Dodge Caravan had one of those trip computers that gave instantaneous MPG readouts (among a lot of other things).

A trip of about 100 miles one evening kept an adult friend totally mesmerized amost the entire trip...."Wow! 99mpg!" "wow! 4mpg!"....

the entire trip....

 

[Rick20]

The only way to observe mpg is total miles divided by gallons used. So one must start full, run 1000 miles, keeping track of the gallons of fuel added, then topping off at the end. I don't have much faith in the dash board computer read outs. Strike that, I have no faith in the dash systems.

You are right kenw, I amuze myself driving trying to make it vary.

 

[darkdan]

I've got a little book in my glovebox that has every fill up for about 2 years now. =)

 

[airbus]

The only way to ACCURATELY measure fuel economy is: #1. make sure your gas tank is FULL (fill it until gas literally comes out of the tank from slight overfill). #2. Make sure you use same gas. #3. Make sure you drive EXACT same portion of HIGHWAY. #4. Keep cruise control on. #5. Make sure its measured at the same time of year (temperature). #6. Do it at least 4 or 5 times. Having said all this,it's all a waste of time because nobody is going to believe you anyways! At least if you are reporting a significany mileage improvement.

 

[airbus]

Forgot to mention how to calculate. For example if you drive 376 kilometers (for us canadians) and it takes 18 litres to refill your tank...18 litres divided by 376 kms= 4.8 litres per 100 kms.

 

[JHZR2]

quote:

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Originally posted by airbus:
Forgot to mention how to calculate. For example if you drive 376 kilometers (for us canadians) and it takes 18 litres to refill your tank...18 litres divided by 376 kms= 4.8 litres per 100 kms.

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Hopefully people at least know that!!!

JMH

 

[airbus]

Don't assume anything!

 

[JHZR2]

quote:

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Originally posted by darkdan:
I've got a little book in my glovebox that has every fill up for about 2 years now. =)

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My grandfather has been doing it since he got his first personal car (they shared one in the family before then)... it was a 51 VW beetle. It didnt even have a fuel gauge.

My mother has done it forever, father has done it forever, and Ive done it since I got my first car too... Fun isnt it?

JMH

 

[daemonite]

i use my smartphone and personal vehicle manager...

it gives me the average, most recent, average fuel cost, distance traveled, total cost, total consumed, overall expense, fuel consumption rate, and cost of ownership...

 

[nickmckinney]

I average about 4~5 tanks to see if the trend stays before I say much of anything. Every tank I get I do the math, and after a while you know what to expect.

 

[airbus]

I've been keeping track of my mileage for years. I feel that it is very important to monitor as it tells you what is going on with your car.

 

[V1]

You haven't seen fuel economy until you've graphed it! Even 1000 miles of analysis doesn't tell you much in the grand scheme of things. You need thousands of miles to show real trends, and real "average."

As I've said here before, I've been keeping track of fuel econ since I bought my car new. The most amount of time I spend "figuring" my mileage is when I type in the numbers off my gas station receipt. Microshaft XL does the rest...

http://tinypic.com/amwc2d.jpg

(IMG:http://tinypic.com/amwc2d.jpg)

 

[pa04prius]

I have the little notebook and calculator in the glove box. I think most owners of a Prius are a little bit obsessed with mpg numbers. I do a running lifetime average and a per tankful calculation. Only real mpg improver I have come across is FP60, that I learned about here. Got me a good 2 mpg over last year when I did not use it. I'm a believer! Oh yeah, been keeping track for over 37,000 miles so I have a real good feel for it.

 

[nickmckinney]

quote:

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Originally posted by V1:
You haven't seen fuel economy until you've graphed it! Even 1000 miles of analysis doesn't tell you much in the grand scheme of things. You need thousands of miles to show real trends, and real "average."

As I've said here before, I've been keeping track of fuel econ since I bought my car new. The most amount of time I spend "figuring" my mileage is when I type in the numbers off my gas station receipt. Microshaft XL does the rest...

http://tinypic.com/amwc2d.jpg

(IMG:http://tinypic.com/amwc2d.jpg)

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Yeah but the problem there is effects out of your control like winter gas, extra weight carried on a trip, sitting in a traffic jam for hours because of a wreck, etc.

Extreme scenario, I can tow a trailer with my truck and get 15MPG instead of 18MPG, but I would not lower my long term average because of it.

My truck gets 18MPG whenever its just me in it, and I am not driving like the south end of a north bound mule. The same truck gets 17MPG when my girl drives it to work, she drives different than me. And thats pretty much how it has been for the last 160,000+ miles that I have owned it.

 

[andyd]

quote:

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Originally posted by JHZR2:

quote:

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Originally posted by darkdan:
I've got a little book in my glovebox that has every fill up for about 2 years now. =)

---

My grandfather has been doing it since he got his first personal car (they shared one in the family before then)... it was a 51 VW beetle. It didnt even have a fuel gauge.

My mother has done it forever, father has done it forever, and Ive done it since I got my first car too... Fun isnt it?

JMH

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HEH, heh, my father starting doing in '57 with a 54 bug that like wise had no gas gauge. they werent std equip until about '61

 

[Gary Allan]

On my wife's ..I always fill it up and I check the mileage continually. It's very stable ..so any improvement over a few tanks would be noticed.

On my minivan I use a spreadsheet that Michael Wan give me. I altered it to give lifetime average and I just input the little receipt that I get out of the pump. Eventually it should even out the variables between one pumping and another.

My mother had a log in her car. I started one with my 02 TJ ..but the wife and kid (oldest daughter) blew that for me. Stealing my ride

 

[TheTanSedan]

As to eliminating variables, don't forget engine hours. As idle time increases, the number of miles traveled drops, and mpg decreases.

Both of our cars have readouts for elapsed time which makes average mph easy to calculate.

 

[bulwnkl]

See my update on my 3,000-mile test of FPC-1 in this forum for a long-term test of a product.