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EV mileage vs gas mileage.


Hardp
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  • 11 months later...

Just to clarify, when I see the following Trip Summary readout after turning off my car:

 

Distance: 19.3 miles

          15.0 EV miles

           2.5 Regen miles

 

...that means I drove 17.5 miles on battery and 1.8 miles on gas?

 

So if I drove the above trip in EV Now mode and the gas never came on, then this Trip Summary readout:

 

Distance: 19.3 miles

          16.8 EV miles

           2.5 Regen miles

 

... should be what I see?

 

I guess the question is whether the "Regen miles" are broken out separately because they are included in the "EV miles" figure or because they're added to the "EV miles" figure?

 

If EV miles + Regen miles = total distance drive on battery alone, then my premise is correct. But if Regen miles are included in the EV miles figure, then for that first trip I would have driven 4.3 miles on gas instead of 1.8 miles, and my assumptions would be wrong.

 

So which is it?

Edited by Blastphemy
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It means you drove 15.0 miles with the ICE off and 4.3 miles with the ICE on.  2.5 of the EV miles were from energy stored in the HVB through regenerative braking. 

 

To figure out how much gas was consumed, you need MPG or MPGe. 

 

If you drove in EV now it would be 19.3 miles total, 19.3 EV miles, and 2.5 Regen miles.   You used plug-in energy for 16.8 of the miles and regenerative braking provided 2.5 miles. 

Edited by larryh
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Bummer :cry: And here I thought I was getting better EV mileage!

 

My Chevrolet Volt and Cadillac ELR would tell me how much gas I used down to the decimal point after each trip. Unfortunately, it looks like I won't know that number until I fill up the gas tank next (which will likely be months) and do the math to see my average gas use. I don't mind driving 4.3 miles on gas if it only uses 0.1 gallons!

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Doesn't MyFord Mobile show the MPG or MPGe for each trip you take?  You can determine the gas consumed from that.

Maybe for 2013s or trips done entirely in ev later. But for 2014s and later it would be very difficult to figure gallons without knowing fords math for mpge for any blended trips. As blended trips are reported in mpge (even though it only says mpg) on MFM for 2014s and later.

 

If the 2015s haven't also had mpg removed from the break down when the vehicle is turned off, and it still functions as in 2014s (mpg only, no e), can use this data from within the car to figure gallons.

Edited by openair
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To determine gallons of gas from MPGe, divide the total trip miles by MPGe to get equivalent gallons of gas.   Then subtract out the contribution from plug-in energy by subtracting plug-in energy (kWh) divided by 33.705.  So if T is the total trip miles, and E is the plug-in energy consumed, then:

 

gallons of gasoline = T / MPGe - E/33.705

Edited by larryh
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post-1636-0-51497000-1433482400_thumb.jpg

 

So based on the 21.3-mile trip shown above that used 5.3kWh of the battery with a Fuel Economy of 60.1 MPG (which is how MyFord Mobile reports it... there isn't any MPGe shown), then my gas used would be [(21.3 ÷ 60.1) - (5.3 ÷ 33.705)] = [0.3544 - 0.1573] = 0.2 gallons?

 

BTW, how do I show attached images at full size in a post?

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MyFord Mobile is showing MPG rather than MPGe.  Plug-in energy is not included in MPG.  So the gallons of gas used is 21.3/60.1 = 0.35 gallons.  That seems rather high.  You will have to see what MyFord Mobile reports for a trip entirely in EV mode.  Is it 999.9?  If not, then the car is actually reporting MPGe (and not MPG). 

Edited by larryh
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MyFord Mobile is showing MPG rather than MPGe.  Plug-in energy is not included in MPG.  So the gallons of gas used is 21.3/60.1 = 0.35 gallons.  That seems rather high.  You will have to see what MyFord Mobile reports for a trip entirely in EV mode.  Is it 999.9?  If not, then the car is actually reporting MPGe (and not MPG). 

 

MFM, for all vehicles that are unable to select MPGe in the vehicle (due to that being removed), are actually reporting MPGe on MFM (even though it SAYS MPG, it is mislabeled).

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MyFord Mobile is showing MPG rather than MPGe.  Plug-in energy is not included in MPG.  So the gallons of gas used is 21.3/60.1 = 0.35 gallons.  That seems rather high.  You will have to see what MyFord Mobile reports for a trip entirely in EV mode.  Is it 999.9?  If not, then the car is actually reporting MPGe (and not MPG). 

 

Here's what today's all-EV trip looked like in the car and on the MFM website:

 

post-1636-0-59971000-1433521782_thumb.gif

 

As you can see, the car shows 999.9 MPG for the trip while the MFM website shows 139.9 MPG. So that means the website is showing MPGe because plug-in energy is being included in the number? And the in-car Trip Summary is showing MPG because it's assuming infinite mileage (because no gas was used) by omitting plug-in energy? Or do I have all of this backward?

 

BTW, almost all the braking for that trip was done by shifting to 'L', so I think that confirms it works essentially the same as in my Chevy Volt and Cadillac ELR (that 'L' slows the car with maximum non-friction brake regen), even thought the spinning braking regen arrows don't appear on the battery when in 'L'.

Edited by Blastphemy
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Yes--the trip summary shows MPG.  So to figure out gallons of gasoline from the trip summary, just divide total distance by MPG.

 

MFM shows MPGe (even though it says MPG).  So it includes the plug-in energy and your calculation in post 9 is correct.

 

Low is not maximum regen.  Maximum regen is 35 kW.  Low regens about 26 kW.  So you can still lightly use the brakes and get additional regen in Low. 

 

You have a rather lot of regen in the previous post.  Normally, one would have 3 regen miles for a trip such as yours.  You must be allowing the car to slow down a lot.  That will decrease mileage.  I try to avoid unnecessary regen. 

Edited by larryh
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You have a rather lot of regen in the previous post.  Normally, one would have 3 regen miles for a trip such as yours.  You must be allowing the car to slow down a lot.  That will decrease mileage.  I try to avoid unnecessary regen. 

 

It's all down hill to work with lots of stop signs/red lights, so the regen was actually increasing mileage. (I compared it to the exact same trip I took two days ago where I only used the brakes and didn't drive as conservatively, and the car was less efficient - I only got 101 MPGe even though EV was 100%.)

 

Also, while I drove very conservatively on that one trip to assure 100% EV, I am in no way, shape, or form a fanatic about driving in EV with the absolute highest efficiency possible. (I would have bought a Tesla if I wanted 100% EV all the time.) I do not hypermile since that inconveniences those around me. Now that I know how to calculate the gas used and am happy with how little is being burned on my regular commute, my car will be set on Auto EV for the next three years and I probably won't look at the stats again. I'll probably have to fill up the tank every 3-4 months, which is not inconvenient at all.

 

Thank you very much for your assistance with the calculations; I never would have found that formula on my own.

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Just to double-check my math one last time, here was my trip home from work today:

 

TRIP SUMMARY from the FFE

Distance: 22.4 miles

          15.9 EV miles

          97.4 MPG

           4.9 kWh used

 

TRIP & CHARGE LOG from MFM website

Distance: 22.4 miles

          15.9 EV miles

          59.3 MPGe (incorrectly shown online as MPG)

           4.9 kWh used

 

gallons of gasoline = T / MPGe - E/33.705

 

Therefore, I used [(22.4 ÷ 59.3) - (4.9 ÷ 33.705)] = [0.3777 - 0.1454] = 0.23 gallons of gas.

 

The trip summary shows MPG.  So to figure out gallons of gasoline from the trip summary, just divide total distance by MPG.

 

Double checking with this formula, 22.4 ÷ 97.4 = 0.23 gallons of gas. So they match. Woo hoo!

 

If that checks out, then my fill-ups (assuming I use 12 gallons before fueling) will generally be every 53 driving days (or about 10 weeks).

 

Thanks, larryh, and everyone else.

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