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About a year ago I started getting anal about recording all kinds of statistics about my cars. So when I bought my Mo, it was no exception. I'm keeping track of everything that I can think of to keep track of.

Below is a screenshot of my "Gas Statistics" Excel spreadsheet. Starts with the very first tank of gas that I ever put into the Mo from day one. The only thing I don't have is what type of fuel was in the tank when I took delivery at 8 miles on the clock! :D

I'll be switching to synthetic oil at my next oil change in another 1000 miles or so, continuing with Premium gas. Then, probably at the following oil change, I'll switch over to regular gas. Just curious as to what will happen.

Some explanation about these numbers:
1) I like driving fast and hard, so consider these "spirited driving" numbers.
2) Most miles so far should be considered city miles, although I have mixed in a bit of highway as well.
3) "Auto MPG" is what the onboard computer calculates (reset each fillup). MPG is what Excel calculates as ColumnF/ColumnD.
4) "AVG MPG" is calculated using "MPG" and is a running average over time.
5) "MPG % DIFF" is calculated as ((G/J)-1)*100, so it is essentially "how far off is the onboard MPG calculation" (Row 7 & 8 are a little off, I think the pump didn't fill up the tank completely on that fillup, so those two lines should probably be averaged out).
6) "AVG SPEED" is what the onboard trip computer calculates (reset each fillup).

I manually enter numbers up to Column H, the rest are calculated cells.

Enjoy! :)
 

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According to your figures, your onboard computer is completely worthless.

Homer
 

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hfelknor said:
According to your figures, your onboard computer is completely worthless.

Homer
Or he's filling up at pumps that overreport the amount of gas pumped to pad the gas station's minimal profits.

I find that the trip computer is usually within +/- 1mpg of the actual amount, thats close enough for me.
 

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hfelknor said:
According to your figures, your onboard computer is completely worthless.

Homer
Not true, Homer. If you compare the MPG column with the Auto MPG column, there's rarely more than a difference of 1 MPG, and most of the differences are .5 MPG or less. Sounds pretty comparable to me.
 

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I do keep some records. And I do like statistic. But nowhere near you! Great job Corin! And keep us posted as we can learn a lot from your experiment.
 

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Discussion Starter #7
TexInFla said:

Not true, Homer. If you compare the MPG column with the Auto MPG column, there's rarely more than a difference of 1 MPG, and most of the differences are .5 MPG or less. Sounds pretty comparable to me.
Correct. Other than the two "off-the-wall" records, the percentage difference is well under 5%. I'm actually pretty impressed that it's that close.

The accuracy of the pump is obviously an unknown factor as well.
 

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Discussion Starter #8
zebelkhan said:
I need to learn a few things from you on record keeping...Good job!
Yes, you too can be obsessive-compulsive if you just work on it a bit! :D
 

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I suspect that someone may have stolen about 5 gallons of gas from my car on a recent trip. Does anyone know if it is easy to open the gas filler door without showing any signs of damage or any other way of taking the gas ?

I took a trip from Seattle to Cannon Beach, Oregon last week . The trip going took about 4 hours and 215 miles. when I got there the gas gauge showed about half empty and the trip computer showed about 24 mpg. I drove the car very little during the week but I noticed the gas gauge was near empty and the gas warning light came on. The trip computer now showed that I was averaging 21.1 mpg, had travelled 287 miles and the DTE was 12. It took 18.6 gallons of gas to fill it up. 287 miles / 21.1 mpg = 13.6 gallons. I seemed to have lost 5 gallons .

When I got home the trip computer showed 240 miles, 24.4 mpg, and DTE 230. I filled up the car when I got home with 10 gallons. The trip computer seems to be quite accurate.
 

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HuskyFan said:
...I drove the car very little during the week but I noticed the gas gauge was near empty and the gas warning light came on. The trip computer now showed that I was averaging 21.1 mpg, had travelled 287 miles and the DTE was 12.
Sounds to me like someone decided to take the car for a joy ride while you were taking a nap...:2: That must have been hard driving too using 5 gallons in 72 miles - 14.4 miles per gallon.....:D

But seriously, if it was stolen gas, then why did your mileage change? It does not take much to clock 70 miles in one week. I bet that is what happened and you just lost track of the miles you drove.
 

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I did drive the 72 miles during the week and my mileage dropped from 24mpg to 21.1. That being the case, I should have been able to refill the tank with about 13.6 gallons, not the 18.6 that it took.
 

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On Board MPG Calculation

How is the on board computer calculate the MPG? My first guess is that it divides the miles driven since last "trip reset" by the amount of fuel spent since the reset. Or, it could compute based on an algorithm that favors the most recent miles driven. Is the information available in any of the manuals?
 

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Re: On Board MPG Calculation

gang said:
How is the on board computer calculate the MPG? My first guess is that it divides the miles driven since last "trip reset" by the amount of fuel spent since the reset. Or, it could compute based on an algorithm that favors the most recent miles driven. Is the information available in any of the manuals?
The ECU precisely meters the fuel that flows through the fuel injectors and I believe thats how the computer calculates MPG. Its not based on the last "trip reset" since you can reset the MPG guage at any time and it will still calculate new numbers every 30 seconds.

The DTE uses the reading from the fuel level indicator with the calculated MPG to give an estimate. Note that when DTE reaches zero, it shows a *, but there is still a gallon or two left in the tank (for safety purposes).
 

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Re: Re: On Board MPG Calculation

Eric L. said:


The ECU precisely meters the fuel that flows through the fuel injectors and I believe thats how the computer calculates MPG. Its not based on the last "trip reset" since you can reset the MPG guage at any time and it will still calculate new numbers every 30 seconds.
If this is the case, then there has to be an averaging computation. Without averaging, you would see 0 MPG if you sit idle, and probably 100+MPG if you coast down a mountain road. So there is still a question of how the averaging is done, (ie. over the last x miles or the last y hours). By the way, some of the BMWs do compute instantaneous MPG and they show 0 MPG when idle.
 

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Re: Re: Re: On Board MPG Calculation

gang said:


If this is the case, then there has to be an averaging computation. Without averaging, you would see 0 MPG if you sit idle, and probably 100+MPG if you coast down a mountain road. So there is still a question of how the averaging is done, (ie. over the last x miles or the last y hours). By the way, some of the BMWs do compute instantaneous MPG and they show 0 MPG when idle.
Its not instantaneous. The MPG computer takes a running average every 30 seconds from the last MPG meter reset.
 

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Discussion Starter #16
Here's an update, now that I'm getting up past 12k miles.

Note how the gas mileage HAS increased over time. The "AVG MPG" column is simply calculating the totals (up to that date) of Col-F/Col-D.

I've also noticed that in the last few weeks my mileage has gone WAY down as the general temperature outside has been going down. My normal commute is only about 4 miles each way, so it's in "cold mode" most of the time during those trips.

(sorry for the quality, files have to be SMALL here)
 

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Discussion Starter #17
By the way, if you total up a couple of those columns you can see that in just 9 months I have done the following:

Used $665.455 gallons of gas
Paid $1870.84 for gas
Driven 12195.1 miles

And that doesn't include the use of my wife's car (which isn't nearly as much use, but still).

Hmmmmmm..... maybe I should stop recording these things... Kind of depressing when you really look at it. :(
 

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Excellent stats!!!

I have been maintaining a spreadsheet with about half of the parameters you list (date, location, $, gallons, & $/gallon).

The depressing aspect of the record keeping is seeing how much money is spent on gasoline. It's depressing!

-njjoe
 

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I haven't been maintaining any spreadsheets....

My commute is 14 miles to the office at 5:45 ish in the morning at 80-85 mph. Two miles are city streets, the rest freeway. On my ride home I get about 5 miles at 80 mph dodging complacent drivers in the left lanes before the great bottle neck occurrs with our lovely trucker road companions merging into the freeway from our city loop bypass. From there it varies from 5 to 45 mph stop and go here and there. The last 1/2 mile is my off ramp which I gleefully get to do some carbon blowout: here I get to see a lot of times what the ricer/fast cars have up against the MO.
:D
Once it was a Viper....couldn't stay with him, but I got to see what a 55 to 100 mph run was like.
Off the freeway ramp it is like a 1/4 mile blast off down to the major thoroughfare into my subdivision. D2 always comes into play here, it is almost automatic to slap it in D2 at that off ramp.....zoooooom up to 55 and drop her over into D. When I turn onto the 4 lane there is a dedicated turn lane which MO eats up at 45 with a little screech down and around to the right; I always experiance some right front wheel lift here if the traffic is kind enough to let me fly--Mo doesn't like that, as I feel some pull go away. Then it is a sporting heavy footed jaunt to my street 1.5 miles later.

That is MO's typical day. I used to get 18mpg when she was new. Then after 10k I saw her go up to 19mpg. I am almost at 20k miles now and she is getting 20-21.5mpg. All that with a heavy foot. The tires are showing my abuse, probably look like 50k on a normal easy going MO driver's tires.

My Toyota 4x4 with a 4 cylinder never got that kind of mileage. If I drove any of my past vehicles like I do the MO on a daily basis, they would get sub 15mpg.

Overall I would have to say I don't think you could have this much fun, in this nice of a roomy, safe vehicle, at this mpg, in any other car.

:D
 

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mgthe3-

Nissan should video the last part of your commute and include it in their marketing campaign. "I don't think you could have this much fun, in this nice of a roomy, safe vehicle, at this mpg, in any other car. " It would be a great piece of advertising.
:D

-njjoe
 
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