Why SUV fuel economy is so much more important than small car fuel economy...

[Formula413]

Is there a way to display L/100KM or G/100M in the fuel logs here at Ecomodder? On the graph and the individual log entries it only show MPG. It would be nice to have a large set of references to essentially "learn" this method of measuring fuel economy.

[TestDrive]

Originally Posted by Formula413

Is there a way to display L/100KM or G/100M in the fuel logs here at Ecomodder?

I don't think so. Fortunately, the math is pretty simple.

100/MPG = GP100M

It's probably something of a chicken and egg thing. People are accustomed to MPG and its hard to persuade them to use something less familiar, so MPG is in the fuel logs. And people remain unfamiliar with GPM, GP100M and GP1000M ratios because they're never exposed to them. FWIW - MPG is a FE (economy) ratio and GP100M is a FC (Fuel Consumption) ratio.

For an example of how the GP100M make everyday, pocket book calculations much more obvious, consider the previously mentioned Car Talk "Puzzler".

Here it is as originally presented.

You drive a gas-guzzling SUV that gets a whopping 10 miles per gallon. Your sleek and efficient spouse drives a sleek and efficient hybrid that gets 100 miles per gallon.

Now, let's assume that both of you drive the same distance each year. Your spouse sees an ad for a new, super-duper hybrid that gets 200 miles per gallon. She is lobbying to trade in her old, wasteful 100-mile per gallon hybrid for the new 200-mpg model; her thinking being that getting this new hybrid to replace the old one will really improve the average miles per gallon of your household.

On the horns of a dilemma, you seek out the one person you trust with questions automotive: your mechanic, Crusty!

"What can I do," you ask, "to improve our household's miles per gallon without buying this new hybrid?"

Crusty says, "Well, if we tune up your old SUV, and inflate the tires correctly, and remove that four inches of accumulated bird poop on the roof, I'm pretty sure we can get you all the way up to 11 miles per gallon." Your heart sinks.

What should you do? That's the question. Under which scenario would your household see the biggest improvement in miles per gallon: by getting the new hybrid, or by tuning up the old SUV?

Get out your calculator then check your answer - Read Click and Clack's answer


Here it is rewritten in terms of GP100M.

You drive a gas-guzzling SUV that gets a whopping 10 gallons per 100 miles. Your sleek and efficient spouse drives a sleek and efficient hybrid that gets 1 gallon per 100 miles.

Now, let's assume that both of you drive the same distance each year. Your spouse sees an ad for a new, super-duper hybrid that gets 0.5 gallons per 100 miles. She is lobbying to trade in her old, wasteful 1 gallon per 100 miles hybrid for the new 0.5 GP100M model; her thinking being that getting this new hybrid to replace the old one will really improve the average gallons per 100 miles of your household.

On the horns of a dilemma, you seek out the one person you trust with questions automotive: your mechanic, Crusty!

"What can I do," you ask, "to improve our household's average gallons per 100 miles without buying this new hybrid?"

Crusty says, "Well, if we tune up your old SUV, and inflate the tires correctly, and remove that four inches of accumulated bird poop on the roof, I'm pretty sure we can get you all the way down to 9 gallons per 100 miles."

What should you do? That's the question. Under which scenario would your household see the biggest improvement in miles per gallon: by getting the new hybrid, or by tuning up the old SUV?

Unless you're truly math challenged, this is not a puzzler. Reducing the SUV's GP100M fuel consumption by 1 is obviously better than a new Hybrid that only reduces GP100M fuel consumption by 0.5!

(Even more obvious, if you can, dump the SUV and you drive the 0.5 GP100M hybrid.)

[jamesqf]

However, miles per gallon makes other calculations easier. As for instance I know I get 70 mpg, and my tank holds 10.5 gallons. So if I'm driving through the middle of Nevada, the gauge show half full, and I see a "Next Gas 175 Miles" sign, do I turn back and fill up at Bandito Gas, the only pump for 100 miles? Or do I drive on, confident in the simple 70 mpg times 5 gallons - 350 miles calculation?

As for the puzzler, its best use is to show the value of out-of-the-box thinking, especially if you're an auto manufacturer. Rather than spend that bailout money on marginal improvements to SUV mpg, you switch your advertising budget to promoting small, fuel-efficient cars.

[TestDrive]

Originally Posted by jamesqf

However, miles per gallon makes other calculations easier.

True, but I don't think the problem cited is a good example.
"1.4 GP100M*, so 2.8 gallons = 200 miles with 2+ gallons in the tank" seems an equally obvious train of thought.

* 70 MPG = 1.42857142857 GP100M or ~1.4 GP100M.

[blueflame]

No need to park up SUV's.

I feel that 95% of the SUV's should be melted down. 95% of their journeys will be 1 person only...

One SUV could make 2 or even 3 smaller cars, that use 2 or 3 times less fuel....

Instead they crushed the electric cars....

[gascort]

Originally Posted by Formula413

Is there a way to display L/100KM or G/100M in the fuel logs here at Ecomodder? On the graph and the individual log entries it only show MPG. It would be nice to have a large set of references to essentially "learn" this method of measuring fuel economy.

+2: Darin/Ben, could this be changed so the first figure is the L/100km and the mpg is the second number in our sigs? Maybe use l/100km in the avatars? Would help us to get used to it.
I'm very much opposed to using Gallons/100 miles. If we're going to switch, do it to units that make sense to everyone.

..I still don't understand why most U.S. Americans refuse to "let other countries impose their units on us"
I guess it is more patriotic for us to stick to the british system of units.

Formula413, sadly, this would necessitate something else to do with your escort-firebirdformula sig inequality wittiness.

[TestDrive]

Originally Posted by gascort

I'm very much opposed to using Gallons/100 miles. If we're going to switch, do it to units that make sense to everyone.

Have you misinterpreted formula413's request? I don't see anything about wanting to replace the existing numbers, just a request for a way to display Gallons/100 miles in each log entry.

I'm absolutely in favor of the USA making a switch to the metric system, but it hasn't happened yet.
In a landscape where fuel pumps read only in gallons; odometers display only in miles; and highway signs show distances only in miles, is it truly accurate to characterize l/100km as making sense to everyone?

Putting l/100km first in the sigs gets an enthusiastic

[Formula413]

Originally Posted by TestDrive

Have you misinterpreted formula413's request? I don't see anything about wanting to replace the existing numbers, just a request for a way to display Gallons/100 miles in each log entry.

Right, ideally these figures could be shown side by side in the fuel logs, this would allow our MPG programmed brains to gain a frame of reference for this new FE yardstick. Getting us Unitedstatesians to learn the metric system is a whole different can of worms.

Originally Posted by gascort

Formula413, sadly, this would necessitate something else to do with your escort-firebirdformula sig inequality wittiness.

Oh well, you can't stop progress. I'll think of something.

[Formula413]

Just an afterthought: if this can be done with the fuel logs, I like Testdrive's idea of using gallons per 1000 miles rather than per 100 miles, since it would generally result in a double digit number, like MPG, and would make the transition easier. And the extra tenth could be added to allow for more accuracy. I think 28.4G/1000M has more of an impact than 2.8G/100M, even though the latter is more in line with practical units of measure.

[trikkonceptz]

Something else not discussed previously is our infrastructure for insuring these beasts. I would have no problem having a pickup truck and a pair of economical vehicles.

However that means I would need insurance for three vehicles in a 2 person household even though the truck is driven 1000 miles a year or less.

A better system would be to insure the driver, not the vehicle, no matter what he/she drove. That way you can hop in from car to car and never worry about insurance.

In my case thats why one vehicle is a wasteful SUV while the other is a gas sipper, it's for that 1 time that I need to haul a show car to car show 200 miles away. BTW the show car has to be insured too even though its driven less than 500 miles a year. So you catch my drift?