The Illusion of MPG: Is It Really A True Measure of Your Car’s Mileage?
All these years, I’ve been doing the simple math of dividing the number of gallons used over a given number of miles driven, to determine how my car is doing on gas mileage.
Now come two professors from Duke University who say that may not be the accurate way to determine how efficient your car really is.
Video blocked at work, any synopsys of the story or a hint on the mathematical formula please? thx
Tis why the europeans have always used L/KM
Those guys are a little conseded if you ask me. their view is the “right way” while every other view is wrong. MPG is not as important as getting less reliant on a country that supports people that want to kill us because we have freedoms.
Hehe,
not only are you guys using arcaeic units you are using them backwards too
l/km = 2.35 / MPG
SI ftw
Wow - Miles/gallon vs gallons/mile - isn’t that the same thing?
The video talks about increasing from 12 mpg to 15 mpg and the amount of fuel saved.
This is all well and good.
The highest MPG mentioned in the video was 50.
Think about how many gallons of fuel would be saved if the MPG was 100, or 200.
Every car I’ve looked at to date seems to top out around 50 mpg. While this would save a decent amount of fuel, I would rather encourage the automakers to deliver a car that gets 100 mpg, rather than convincing themselves that 12->15 is amazing.
Yes the numbers translate 15 mpg is x gallons/mile and 12 mpg is x+y gallons/mile - but I don’t believe that 12->15 is amazing.
Show me 100 mpg - that should translate to a truly amazing gallons / mile.
This video might help convince a few friends who get bad mileage to switch up.
Example: If you drive 15,000 miles per year in a 10 MPG sport-utility vehicle you could save ~350 gallons of gas every year by driving a 13 MPG car. That is $1,400 in your pocket!
The same 3 mpg increase from a 25 MPG car only saves you about 65 gallons of gas ($260).
The people with the least efficient cars have the most economic incentive to improve.
Nice. I’ve never realized why l/km was used instead of mpg.
Linear vs. logarithmic methods?
For those blocked video folks: small increases in mpg at low levels (for instance from 12 mpg to 15 mpg) will make a huge savings over 100km, while increases at more efficient levels (for instance, over 25 mpg) make less of an impact on gallons used.
The video’s example: 10 mpg = 10 gallons used, 20 mpg = 5 gallons used, 25 mpg = 4 gallons used, 50 mpg = 2 gallons used. Going from 10 to 20 mpg saves 5 gallons, but from 25 to 50 mpg only saves 2 gallons.
Yes, the more informative way to report fuel useage/economy is as the Europeans do it: liters/100km; in an American version, gallons/100 miles.
Concerning the fuel savings of hybrid SUVs Prius Maximus has pointed out the following:
“Here’s the correct way to look at these ’savings’ [gas used while driving 1000 miles]:
666 gallons [used by an SUV] - 222 gallons [used by a Prius] = 444 gallons wasted by the SUV driver
It’s not how much you save, it’s how much you use.”
Of course, the Duke Prof’s didn’t ask the final, most important, question - What if you replaced a vehicle that gets 10 mpg with one that gets 50 mpg? or even 100mpg?
This video leaves (some, maybe even the vast majority of) people with the impression that, if they replace their 12mpg gas-guzzler with a 15mpg gas-guzzler, they will have done their part.
That is wrong.
Sorry you are all off base. Both gallons and liters are units of volume and as such are subject to change with TEMPERATURE! So on a cold day you get more ‘energy’ per unit volume than on a warmer day. A better way in which to measure fuel efficiency is on a mass per unit distance basis. Use kilogram per kilometer for example but don’t make the common mistake of thinking that a pound ( lb ) is a unit of mass…it is a unit of force ( mass x acceleration ) as it includes the acceleration due to gravity.
But even that begs the question of energy efficiency. Different fuels have different ‘energy densities’. An attempt to do this is the ‘octane rating’ of fuels. It doesn’t work well at all. For example in Brazil cars all run on nearly pure ethanol; 85%. But the mileage for pure ethanol vs gasoline is a factor of 1.5 LESS! Yes, ethanol is not a great fuel when put on this basis. A better standard is needed and arguably we don’t have one now.
IMHO a much better unit of measure would be COST per unit distance. Say, $/mile or EU/kilometer ! For most of us, fuel efficiency isn’t the bottom line, it’s cost to our pocket books. Or even ask the question, how many hours must I work to travel one mile??
With all the options for fuel right now, we really need an accurate manner in which to compare them! Then we can get on with the rest of the ‘paradigm shift.’