MPG onboard calculator

[Castrosua]

So what no more cable coming from the tranny? lol. Actually, this cant be from 20 years ago, since my Crown Vic has a cable driven odometer.

But, what about burnouts? Conceivably you could have a car with 1000miles on it done through burnouts alone. Is that truly 1000 miles or less? (silly joke here)

[2013 ZL1 #7860]

Mine says 4.9 mpg... Perhaps it is broken?

[Castrosua]

Originally Posted by Comrando

Holy moly. Your odo-meter went to 12,000 miles with no user intervention?

I have a 1974 Matador with 8 miles if you are interested.

Huh..what? Im a bit lost. The Camaro? I dont even know how to "intervene". Even on my Crown Vic, I can just attach a powerdril and just spin baby spin. I dont because Its my car and Im never giving it up. Hence how it's totaled with a clean title because I never gave it the insurance, so I just fix it up and good as new...

As far as the other records, well Im going to post now, so be prepared to be amazed or mentally chuck stuff and me

[Angrybird 12]

Originally Posted by Splitter

Hand calculated is the way to go.

Onboard DIC adjusts your MPG every second the car is on an operating, if you idle for one minute, it will factor in one full minute of 0 MPGs

What hand calculating cannot take in account is density and volume changes due to temperature variations between fuel fill and empty. It also does not take into account the pumps accuracy that you fill at. Yeah they are supposed to be calibrated but even at that calibration can get off between official calibrations.. I worked for 32 years in instrumentation and calibrating flow meters was part of it. What may show 10 gallons today may show 10.5 gallons next month depending on wear of the pump's flow measuring equipment.

Also because of wear of your injectors the DIC reading can also change over time.

So use both as a reference because neither are 100% accurate all the time.

[Castrosua]

So heres a pic of each car's maintenance book. (at the time only 3)


Top Left: Crown Victoria LX Sport (still waiting on official word if its a 1 of 1 car. Even if its not, its still going to be one of the rarest CVs you can ever get) The normal day to day log book.
Bottom Left: Same car but with transcribed logs. So I dont have to open a binder that big just putting in gas. It stays in the trunk in case I need to look up something that I did way back when.

Top Middle is the 72 Continental's book. I put the printed pics for fun, but that one was from the third party seller in Ada MI where I got here. It has the winning ebay bid (mine duh) and thought it was cool.
Bottom Middle same care and same transcribed logs. I do this when the 781D section gets too big (from Air Force form 781, aircraft maintenance logs). I transcribe the write-ups to the new packet, if its a job thats open it gets transcribed, if its closed (as in corrected) thats it, it stays in the old forms that go in the big binder.

Right is the daily book for the 73. No transcribe book at the time, but I do have one now. So the same thing.

This is the 781F (for fuel, the suffix letters are different from the real AF numbers. So if anyone her was an aircraft mechanic in the AF dont kill me lol) So you can see each block in two columns with 4 rows.(the bottom is easiest to read in the pic.)
Top row is: Miles(odometer reading), Trip (trip odometer) Date (YYYYMMDD, so in a computer if you use sort by name, it goes oldest to newest) Number (as in how many times was the car fueled up. I only do full tanks to help with calculations of MPG)

Bottom row of each fill up is: Gallons (how much to fill), MPG (calcuated usually later on. Im not going to calculate that until I transcribe it to digital backups),Price (as in how much per gallon), Octane (obvious)

This one is from my 72. The lowest mpg on that page is 8.07. That was driving around McGuire AFB, and anyone thats been on an AF base knows, you dont speed at all. 25 means 24. 15 (yes, 15 in housing) means about 10lol. But right above I got 19.92 coming down the Turnpike, doing 75-80. Not bad for a nearly 50 year old car weighing in at 5200lbs.


Here are maintenance actions. Each page can document three actions.
On the left is the complaint/defect/problem (hence why i call these 781P for problems) and on the right is the corrective action.

Each of the three have slots for mileage when occured, when fixed, date discovered, date corrected, even a slot for work order numbers (If fixed at a shop, I can look that up without the receipt on hand, which I keep anyways)

I sign the bottom to know the job is completed (like the block in the middle) Also when a job is fixed I write down the refference from the applicable shop manual IAW (In accordance with...page number para of whatever used)

The little box in the top left is for the symbols. Each writeup comes in three types.
-- (long dash, or if typing two regular dashes) In red usually (carry over from the AF. Its why the joke about AF crew chiefs is what does a crew chief use to fix a jet? a red pencil!) back to the dash. It means an inspection writeup. As in an inspection is required, and if anything found then more write-ups follow referencing the inspection by page and block

/ (diagonal line, again in red if possible) means write-up that does not affect safe operation. As in you can drive with the car with this write-up. Like air conditioning, or a bad bearing. Diagonals can be upgraded to a more serious condition if not fixed soon

X (red x. I still call them that, even if they might appear in normal ink) dangerous and grounding condition. So flat tires, blown head gasket, meteor hits the car lol

All writes ups have a unique packet number, page and block too.


781D (from the original delayed discrepancies) or TCTOs (time compliant tech orders) as in things that occur periodically. So oil changes, trans flushes (which I do on my CV, even well over 100k, since ive always done them on that car. Other cars that Ive got used, no, you let it be)

These are backed up on an excel spreadsheet, since the forms only have the last three, just as refference. I check this periodically and see whats coming up next. Some items have mileage some date or both (like oil changes now, since I cant drive and put the miles on 5 cars)

Once an item like oil change comes up, say im at 299000 miles and its due at 30k, I put the red diagonal in the 781P's and then once its done i upgrade to a red X since you can drive the car in the middle of an oil change. No oil, no drain cap, filler cap. So if I stop or am interrupted I know theres a grounding condition. (I also have tags with each symbol, and the highest one gets tucked in the cover of each daily binder)

I also have my own inspection checklists 3A and 3B (similar to before and after flight inspections, only mine are spring 3A and fall 3B. They have slight differences since a 3A comes right after winter, it might need special things to look into, where a 3B after driving all summer, I might want to check on things that could have worn. Brakes wont wear out while sitting over the winter, and differentials may seep and lose fluid while driving)


Here are the tire tags. each wheel has an assigned number. With tire manuf. model and size of course (not that can change unless modified) Each position indicates the position on the car. This was easy to follow when each tire had a unique serial number, but lately Ive noticed that not all tires have such a s/n. On steel rims, I just pain stick on the backside the appropriate number (out of sight so it wont affect originality.)
I also note any defects and such, like on my 72 you can see in the pic, tire 4 (driver rear) has a spring lodged in the tread. No leaking so I dont touch it.
The spare is there too, the lowest one. (on the 72 its an original spare that I have the michelin warranty papers for too, so a big DO NOT USE is on that tire tag)


Heres the 781P in word. Some "problems" may come with multiple write-ups with an FOM and a page and block. If youre replacing lifters and need to pull the manifold out the manifold being removed will red X (ground) the car obviously. The worn lifters are just a red diagonal. Ive had one action requiring a few pages worth of other writeups.

You can see above R2 (removed and replaced) as in swapping a part with another one. If its just removed and put back its "reinstalled". You can see the IAW here better, followed by the chapter page para from the shop manual.

When a writeup is closed out, thats when I sign the bottom of the corrective action side and initial over the symbol. In word I just color it over the symbol with gray.


781M is the modified stuff. I imagine with my Camaro it will be a bit more extensive that what Ive done to my 72. Its all original minus stuff like fuel lines for ethanol gas, valve guides for unleaded gas, tires like 235/75R15 instead of 225X15 tires, rubber valve cover gaskets instead of cork, an aditional fuel filter before the pump and so on.



The last one for now is the fuel file for the 72 Continental, the same like all my other cars, containing everything the 781F's have.

So that escalated quickly...but I did say Im OCD. Ive been told that the level of documentaion on my cars actually brings the values up considerably. Ive had offers for 25k just last year for my Crown Vic, and part of that was the records, not just the condition and how clean and oringal the car is (still have the protective plastics on electronics on the dash, and I have spares when those fall off lol)

So, koodos to anyone that actually read thought this lol and awesome if anyone found it interesting and might do that to their cars. Camaros need loving and caring like this as much as they yearn to a good pounding of asphalt!

[jimlem]

Originally Posted by Castrosua

So most of you dont care about MPG's which is perfectly ok. (now smiles per gallon different story ) Hell, I got a few classic Continentals, that I do drive quite a bit.

But I do like to keep track of MPG's and just about everything else in all my cars, in maintenance binders as well as computerized form (excel and word files)

Anyways, back to my main question. How is MPG calculated onboard? I figured it was an estimate and was expecting it to be within a percentage of real MPG but....



So I do this for all my cars, document mileage among maintenance actions, any modifications if any, oil consumption tire condition and placement. Its just a good practice to set baselines as far as consumption so if any time numbers dont match up, I can start looking into things. It helps on cars without ODB or computers. So dont jump on me with the whole "get a prius if you care about mpgs )

Also some of you that were in the Air Force working with aircraft, yes thats where the 781F comes from. I was a crew chief, so its how I modeled my car books and digital records, from 781 forms.

So now that all that is out of the way. There is a discrepancy between real world numbers and displayed mpg. The max variation Ive seen is about 4.69 percent to as close as to 0.734 percent to real world. I cant see a noticable pattern, so the only thing I can imagine is that if this is GPS derived then weather, signal, and various errors in how position is calculated that make up the error Ive seen so far.

So, anyone noticed this or cared? I know Im kind of powergeeking it here rolled up in a blanket of severe OCD, but I am curious what sort of numbers you guys and gals have seen.

Al

Can you show your formula for column F (MPG)? Thanks

[Castrosua]

Its B/E so Trip/Gallons

[BLU DUCE]

[QUOTE=Castrosua;8430343]I didnt think of that, the gas in the hose. I just thought it was interesting to compare. I always log mileage and always do complete fill ups. On all my cars, and I might be one of those rare people that use the trip odometer. It can get a bit tedious keeping records on 4/5 cars (well 4 and a quarter since the 5th is a parts car and its pretty much just a shell now, but hey, got a title and keys to it lol)

Anyway, I just like knowing as much as I can about my cars, especially when they are new and I havent had a chance to get intimate with em hehe.... I didnt know squat about my Crown Vic until I got a parts car that I tore apart. No I KNOW em inside and out. In 10 years when Ill be ripping my 5 (if I still have it) then Ill be a Camaro expert too![/QUOTE/]

Something a lot of people don't know about. I use to drive gas tanker. The temperature of the in ground tank is the same as your vehicle tank. When you put gas in your car fill it slowly you can actually get any where from a 1/2 to 3/4 of a gallon more.

[Castrosua]

Didnt know that trick. I do know to fill up when its cooler outside so you dont lose much to evaporation on a hot day

[VTXrider]

Originally Posted by ChrisBlair

What I'd like to know is just how the rated MPG is determined for 'city' driving: how many stops and for how long, for any period of time. Way too subjective for my taste. I can drive through Boston at 4 am and get 17 mpg, and then at 4 pm on the same route, get 8 mpg.

If you go to http://www.fueleconomy.gov/feg/how_tested.shtml it explains it.

Long story short, there are a series of very specific test that all cars go through in a laboratory setting. They take the cars through very specific routines with specific rates of acceleration, speeds, and stops. Then they take this data and adjust it by a specific formula meant to adjust to more real world conditions. Nothing in this is subjective, however none of it will match how you use your car either, we all have different traffic patterns, road, and weather conditions we drive in.

[PalmerGA]

You're right, OP... I don't care. All I know is I can afford to fill up whenever necessary. On long trips (400-500 miles or more), I pay attention to the mpgs shown on the DIC. I have compared to hand calculations and it is well within 5% either way. If you travel at least a tank's worth of distance and reset your mpgs from the start, you'll be pretty close to reality.

[Castrosua]

True, another thing is that you need the car running during fuel up, so depending on when you shut off it may affect when the decimal changes (after you reset).

For me it may not be about money, but I do like knowing if anything is off based on mileage, if an engine code isnt thrown, or if I cant hear of feel an oncoming problem. Granted for even the oldest 5th gen, these arent big concerns since these cars are still new

[Mels RS]

I filled out my share of 781s in the Air Force.
I keep maintenance logs on my cars just like I do on my aircraft but not nearly as detailed as the 781 forms.

[LoneCynic]

OP, I'm not nearly as detailed as you, but I am fairly serious about logging information about my two newer vehicles. Each one has a journal book in the glove box, with sections marked out for fuel log and maintenance log. Much of that same information I record there in pencil:

Fuel Log:
Date/Gas station name/price/octane/gallons/mpg/trip1/odometer

Maintenance Log:
Date/Service location/Service performed/trip2/odometer

Then I have an accordion filing folder to keep all the service records in, in order, by year. All of this is in the glove box of each vehicle.

How much variance between my hand calculated MPG and the one in the DIC? I'm not sure, I never look at it.

I have an older pickup too, but I'm the second owner of it, and it is over 100k miles. I used to keep detailed records for it, but I got away from it. I blame my youth at the time with that one. I do everything for it myself, so when I change the oil and rotate the tires, I just rip the tab off the oil filter box and write down the date and stuff done and stick it in the visor to reference when I think I might be getting close to the next interval.

Your dedication is admirable, I wish I was detailed enough to do a spreadsheet as well. I suppose I always could, so long as I keep my hand written records up to date.