10 to 12 mpg improvement is the same as 30 to 60 mpg

[theycallmeebryan]

The problem only lies when you think in terms of MPG improvement.

MPG number increase does not illustrate how much VOLUME of fuel is saved.

When you talk in terms of fractions, it works, but still doesn't illustrate the VOLUME amount saved.

[ecomodded]

Maybe the mericains could do it by "quarts a 100 miles"
or does that sound ridiculous to those south of my border.
I know i would be confused by it..

[Fat Charlie]

Originally Posted by Old Tele man

since, there are many low-MPG vehicles and relatively few high-MPG vehicles, more progress (benefit) arises from small improvements to the many vehicles, ie: the benefit of the multitude over the benefit of the few.

Even if there were more high mpg vehicles than low mpg vehicles, a slight improvement in the Elantra will result in a little less gas burned for every 100 miles traveled. A slight improvement in the Suburban will result in a lot less gas burned per 100 miles traveled. Say Bob gets 40 mpg in his Elantra. That's 2.5 gallons burned for every 100 miles he drives. Move heaven and earth to get his car up to 45 mpg and now he's burning 2.2 gallins for the same trip. Joe gets 12 mpg in his Suburban, burning 8.3 gallons as he follows Joe. If they get that Suburban up to 14 mpg, he's "only" going to burn 7.2 gallons for the trip. Now a 5 mpg jump in the Elantra saves us 0.3 gallons while a 2 mpg gain for the Suburban saves us 1.1 gallons. If I rounded the Suburban's gain a smidgen the other way, you'd need 4 Elantras on the road for every Suburban to get the same overall benefit. We don't have that kind of ratio, and anyway I don't think Hyundai left 5 easy mpg lying around. GM could find 2 if they bothered to look.

ecomodded- When y'all Canucks phrase the speed limit in "minutes per 100 km" to match your l/100 km then maybe we'll think about changing our mpg and mph.

[gone-ot]

FWIW--that was a "macro" statement about all cars, not a "micro" statement about a single individual's car (wink,wink).

[ecomodded]

Fat Charlie we already measure our speed with a widely used and accepted method,Metric. Some day America is going to get on board with the Canadian and European countries.

Until then it could be quarts a 100 miles for you guys.. for practice for when metric becomes your standard.

[gone-ot]

...sorta like "...furlongs per fortnight..."?

[theycallmeebryan]

A picture is worth a thousand words, as they say.


The axis on the bottom is arbitrary. This graph illustrates the relation between MPG and Gal/100m

[briank]

I suppose one advantage of the use of mpg is that a given actual load reduction (ex. 200 N less of tractive force) or an engine efficiency increase (ex. 1kWhr/gal increase) translates to a much higher mpg jump on an already high mpg vehicle than on a low mpg vehicle. Or put another way, at least to the general public (who think linearly), the use of mpg somewhat counters the diminishing returns of harder to implement efficiency improvements because the mpg value amplifies these small improvements - which may be on the whole a positive thing. Just think of the mpg boost an already high mpg vehicle will get, when an engine with constant compression ratio regardless of load comes to market, that is if ICE continues to be the power source.

[jamesqf]

Originally Posted by ecomodded

Fat Charlie we already measure our speed with a widely used and accepted method,Metric. Some day America is going to get on board with the Canadian and European countries.

Until then it could be quarts a 100 miles for you guys.. for practice for when metric becomes your standard.

Two different issues, and let's not argue about metric. Measuring fuel consumption in your inverted "liters per 100 kilometers" fashion just doesn't make sense, and that lack of sense is the same* whether it's quarts per 100 miles, gallons per league, or whatever. If I know that I get 70 mpg, and it's 350 miles to where I want to go, I know instantly the useful fact that I will need at least 5 gallons to get there. Give me that same number in liters/100 km (or gallons/100 miles) and I have to do some math to get a useful answer.


*Then there's the other senseless thing about your l/100 km: that it uses 100 km instead of just 1 km, or 1000 km. Supposedly the point of the metric system is to have units scaling by factors of 1000, yet this breaks that.

[Kodak]

Originally Posted by Fat Charlie

Finding a way for the next gen Prius to get 2 mpg higher on the EPA test won't make as big a dent in gasoline usage as requiring 1/4 ton pickups to get 2 mpg higher on the EPA test. That won't make pickups green, but it's where the industry should focus its FE efforts.

I agree with your logic, but differ on your implementation.

If we could keep the current fleet, but encourage more drivers to use even the most basic hypermiling principles, we could have the same effect without building any new cars or legislation.

I'll go one step further and say that this reasonable 2 mpg improvement could be encouraged with some ideas from our traffic flow thread (about the most FE-detrimental traffic policies) - even if no drivers give it a second thought. They'd just think "Hey, I'm hitting fewer red lights - it must be my lucky day!"