Fords mpg is a lie

"My bird IS the word" (mybirdistheword)
07/07/2019 at 12:55 • Filed to: None

So I was messing around with my trip computer, I wanted to see if my mpg was increasing with break in.

The damn thing was dropping at the red light! Ford apparantly thinks idling should count for mpg, even though it consumes remarkably little gas!. This means I have been getting better mpg than I t hought, sure. It also means I have to calculate this shit by hand.

DISCUSSION (21)

ToyotaFamily > My bird IS the word
07/07/2019 at 13:10

I don’t think I’ve ever owned a car that has a reliable MPG calculator. My 4Runner’s was saying about 21, was much closer to 16.

Dr. Zoidberg - RIP Oppo > My bird IS the word
07/07/2019 at 13:11

I only calculate by hand and I consider it the only trustworthy method.

MarquetteLa > My bird IS the word
07/07/2019 at 13:13

Well your real-world MPG is literally just how much fuel you consume while the car is on. So if you are using fuel to keep the motor running at idle, but you aren’t covering any distance while doing so (at a stop, versus coasting) your MPG is zero. Why wouldn’t that be accounted for in the figures your car is showing you?

BrianGriffin thinks “reliable” is just a state of mind > My bird IS the word
07/07/2019 at 13:15

Yeah, i don’t get it. Of course idling counts; you’re getting 0mpg while sitting there.

MarquetteLa > MarquetteLa
07/07/2019 at 13:18

This is all about averages. You only have one mile on that tripmeter, which is the only data being taken into account on that trip MPG readout. The more time you spend idling at a stop, the more fuel you’ve spent going nowhere (zero). When those zeroes are added into the average with your one mile of actual driving data, your trip MPG goes way down. You have to keep your own data if you’re trying to get real results from your numbers.

Tekamul > My bird IS the word
07/07/2019 at 13:34

According to DoE research, on average idling in urban environments is responsible for ~17% of fuel consumed.

Idling while sitting at a red light should absolutely be reflected in the calculations .

https://upload.wikimedia.org/wikipedia/commons/0/05/Energy_flows_in_car.svg

My bird IS the word > BrianGriffin thinks “reliable” is just a state of mind
07/07/2019 at 13:35

It does but it shouldn’t be dropping by that amount. Its calculating twice: mpg is an average of fuel consumed and distance, its like the car is calculating the instant mpg spit out by the ecu and adding the time spent at each mpg value instead.

My bird IS the word > Tekamul
07/07/2019 at 13:37

But i didnt use 2 miles worth of fuel at a 30 second stop light.

My bird IS the word > MarquetteLa
07/07/2019 at 13:39

I just think the computer is calculating it wrong. Theve done tests on whether it takes more fuel to start a car or idle it and idling really doesnt use much gas.

dogisbadob > My bird IS the word
07/07/2019 at 13:55

All cars get zero mpg when idling

Gerry197 > My bird IS the word
07/07/2019 at 14:02

Trying idling in a 5.7L Hemi, moves down pretty quick. Also, it’s averaging based on your total mileage since reset, how many miles did you cover when you noticed this drop?

Also, trip computers are only for approximation , some are optimistic some or not. I recommend you use a mpg app to keep track of your actual mileage.

DipodomysDeserti > My bird IS the word
07/07/2019 at 14:07

That’s not how math works.

E90M3 > My bird IS the word
07/07/2019 at 14:50

Did the MPG average reset when you reset your trip odometer? If so, only driving one mile then idling at a stop light for a half a minute would affect calculated MPGs that much because it’s such a small sample size.

BrianGriffin thinks “reliable” is just a state of mind > My bird IS the word
07/07/2019 at 14:54

But the car is making the assumption that past behavior will lead to the same future behavior ad infinitum. It doesn’t know when or if you’re ever going to start moving again.

Captain of the Enterprise > My bird IS the word
07/07/2019 at 15:51

I just calculate by filling up all the way and checking the gas I filled up to the miles covered. My cars haven’t had a mpg calculator.

My bird IS the word > E90M3
07/07/2019 at 17:54

Yes but I figured it would update when I drove additional miles, not at a dead stop. This makes me think its not running the right calculation.

My bird IS the word > DipodomysDeserti
07/07/2019 at 17:56

Miles/gallon, not ecu mpg/time spent at each mpg

DipodomysDeserti > My bird IS the word
07/07/2019 at 18:15

Sounds like you’re looking for an instant mpg calculator. Which in this case would read 0 mpg while you were idling.

E90M3 > My bird IS the word
07/07/2019 at 19:13

It’a adding a bunch of 0 MPG data points in there since you’re currently getting 0 MPG. If it’s got a 1000 miles of data points, idling isn’t going to change much. If you just reset it, it’s going to have a much larger impact.

Tekamul > My bird IS the word
07/07/2019 at 20:13

Am I reading the display wrong, or had you gone 1 mile on the trip meter? If that's reporting MPG for the trip, then it's saying you had burned 1/23.2 of a gallon when you came to the light, and roughly .0015 gallons while you were at the light between pictures. Seems pretty plausible.

If only EssExTee could be so grossly incandescent > My bird IS the word
07/07/2019 at 21:36

Doesn’t use much gas, sure, but it still uses gas. Fuel economy is an equation, distance/fuel use = economy . When you up the “fuel used” value without upping the “distance travelled” value, the final economy number gets smaller.