Considering the Start/Stop time when looking at MPG

[SacRebel]

There are dozens of threads talking about the poor gas milage of the trucks. I for one am only getting <12 mpg in mine. This got me thinking about the Start/Stop feature and how it plays a role in the mpg. Obviously the mpg calculation is based on actual miles driven but doesn't take into account idle or when the engine shuts down.

I saw a video a few weeks ago where someone was saying the older Hemi engines used 1.7 ounces of fuel during 90-seconds of idle. I don't know if that's true or not but there is some fuel lost during these idle times.

So with this said I think we also need to take into account the Time between fill-ups in addition to mpg. I know in my '04 1500 with a Hemi I would get around 6-7 hours (same mpg and primarily city driving) between fill-ups (same tank size). Since my truck only has about 500 miles on it it's too soon to get a feel for the number of hours between fill-ups. But I will certainly be taking that into account before whining about the poor gas mileage.

 

[slimchance]

i guess i am not quite sure what you are getting at when you say ... "Obviously the mpg calculation is based on actual miles driven but doesn't take into account idle or when the engine shuts down. " ...
to calculate mpg you divide the total miles driven by the gals used .. this calculation includes the gas used during idle since the engine is using gas even though you are not moving at idle .... you do not get to remove the idle time usage from the mpg .... or am i missing something here
so in your way of looking at mpg, i refilled my trk 2 weeks ago (drove it 4 hrs) and since have driven 200 miles and have used 10 gals of gas, therefore my average is 20 mpghrs .. i just do not get what you are driving at
when your engine is running at idle sitting at a light you can see your average mpg dropping because the engine is using gas but not moving .... when your engine shuts off while sitting at a light you do not see the average mpg dropping because the engine is not using gas AND is not moving

 

[Bleda2002]

Yes, this mpg meter does take in to account idling, including remote starts. My F150 gauge loved to lie by not counting my time idling in park. It used to tell me I was getting 17.5 when by hand it was more like 16 since I do a lot of idling

 

[Gondul]

AVG MPG will drop while sitting and idling in traffic... I know, I watched it go down quite a bit some months ago.
I have one or two lights on my way to work that are hideously long... if I get caught right when they turn red, I just shut off the engine and wait.

 

[davis2885]

These trucks take into account idle. i know mine certainly does when I remote start it to warm up.

 

[DeanKing]

An idling vehicle lowers mpg. One that is shut off does not. So In a weird way the OP is correct. The MPG does not account for time in start stop. Don’t think of it that way. If you did not have that feature your MPG would be lower. In theory. I wonder how much the 90 lb battery pack and electric motor lowers MPG. It can mess you up thinking about the possibilities.

 

[SpeedyV]

An idling vehicle lowers mpg. One that is shut off does not. So In a weird way the OP is correct. The MPG does not account for time in start stop. Don’t think of it that way. If you did not have that feature your MPG would be lower. In theory. I wonder how much the 90 lb battery pack and electric motor lowers MPG. It can mess you up thinking about the possibilities.

Well, 90 lb / 6000 lb (ballpark) = 0.015 = 1.5%

1.5% x 16 mpg (ballpark) = 0.24 mpg

So purely in terms of weight/mass...not much. And if eTorque provides a net gain of roughly 2 mpg, then it’s providing a lot more benefit than weight penalty.

 

[Electrical]

Time between fillups as a metric... interesting idea... thumbs up for something thoughtfully different.