All this fuss about mpg and gpm

Tim Folkerts

Super Moderator
#11
The idea of "Fermi problems" is well-known in physics circles, and I think it is a skill that many, including managers and quality professionals, should practice. Also, to describe a Fermi problem, rather than saying "making intelligent estimates when little or no data is available" I would say "making reasonable estimates using diverse knowledge that an intelligent, well-informed person might possess."

The goal is partly to come up with a reasonable estimate, partly to know when numbers just don't make sense, and partly to think about what information might be needed to solve the problem. The piano tuner question is a classic example. Drops of water in the Atlantic Ocean is another. My estimate of the probabilty of a head-on collision in a previous thread is another. In a business setting, you might ask "what is the cost to produce this widget?" or "what is the potential market for my new product?" After all, if you are planning to build a better mousetrap, it would be wise to have at least some idea of how many mousetraps people need and what they might cost to produce! Or if you have 100 potential 6S projects, it would be wise to make a rough estimate of savings to narrow down the choices and then do a more accurate estimate on the remaining projects.


Tim F
 
Elsmar Forum Sponsor
J

JerryStem

#12
My 1993 Eagle Talon got good gas mileage when it was new. I'd guess ~20-25 mpg average. Now after 200k miles, I'm sure it's less.

Now I'm looking at Scion Xb's. They are rated pretty high for a sort-of SUV thing (hard to say what they really are...) I think in the range of high 30's mpg, city and highway.

I know when it also has 200k miles on it, it will be less (even though I plan to take great care with it, I tend to keep cars as long as possible).

But, just give me a decent comparison of Xb's vs. Honda Elements vs. Saturn what-evers, etc... Don't confuse the issue with possible changes over time depending on useage, where driven, maint. performed, moon phase changes, etc...

I've treated mpg with a grain of salt in my ~20+ years of driving anyway...

Jerry :rolleyes:
 
C

Charmed

#13
JerryStem said:
My 1993 Eagle Talon got good gas mileage when it was new. I'd guess ~20-25 mpg average. Now after 200k miles, I'm sure it's less.

Don't confuse the issue with possible changes over time depending on useage, where driven, maint. performed, moon phase changes, etc...

I've treated mpg with a grain of salt in my ~20+ years of driving anyway...

Jerry :rolleyes:

Dear Jerry:

OK, we won't confuse the issue with possible changes over time depending on useage, where driven, maint. performed, moon phase changes, etc... But, why have you treated mpg with a grain of salt, Jerry?

Can you add some insight here?

Charmed :) :thanx: :thanx: :thanx:
 
J

JerryStem

#14
Price and reliability mean alot more to me than MPG. If one car is rated 23 MPG city and the other is rated 27 MPG city, I don't care. Which is $2k cheaper? Which one has a better track record for maintenance? Which one has a better resale value?

I'm not sure how the estimates (right there, "estimates") are made, but I'm sure it won't be "dead-nuts-on" in my experience anyway. To me, there's many other comparisons to make.

Jerry
(Ok, one's rated 18 MPG, the other's 53 MPG, then I start paying attention...)
 
U

uk2china - 2008

#15
Cheap at half the price......

Marc said:
$2 is potentially too wide a variable.
It certainly is when we are about to hit $7.20 (UK£4.00) per gallon.

:nopity:

regards

uk2china
 
C

Carl Keller

#16
Just an observation:

There usually isn't a great disparity when comparing MPG and type of vehicle, when all other factors are similar.

If You compare "economy" cars with similar sized engines between manufacturers, they are within a few MPG.

Similarly, if you compare large SUV's with V8's of similar displacement, they are going to have similar MPG ratings.

I can't think of an instance where a vehicle get's say, 16 MPG and a competitor gets 24 MPG.

This is another reason people do not shop based on fuel economy. The type of vehicle already dictates the MPG "range" they are buying into.

Carl-
 
C

Charmed

#17
Type of vehicle and mpg

Carl Keller said:
Just an observation:

I can't think of an instance where a vehicle get's say, 16 MPG and a competitor gets 24 MPG.

This is another reason people do not shop based on fuel economy. The type of vehicle already dictates the MPG "range" they are buying into.

Carl-
Dear Carl:

You are absolutely right about type of vehicle and mpg. The automotive industry is very competitive and they match every feature the competition has to offer.

Except, now the Toyota and Honda are again upping it with hybrids. There are many comparable priced cars - without the hybrid option - offered by Toyota Prius, Honda Insight, and now the Ford Focus Escape. The production and supply of these hybrids is now limited. I have read reports that Toyota wants to sell 300,000 hybrids by 2005. When that happens and customers begin to get used to higher mpg, for a $25,000 to $30,000 vehicle? Things might start changing.

Then, of course, all the other manufacturers will follow suit. But, who will have the advantage in terms of (perceived, or real) quality and reliability and therefore increased sales in this new segment? My next car might just be a hybrid.

Charmed :)
 
C

Charmed

#18
uk2china said:
It certainly is when we are about to hit $7.20 (UK£4.00) per gallon.

:nopity:

regards

uk2china
Dear uk2china:

In the US, the gasoline prices have actually being going down, even as crude oil prices have gone up. The crude price has just recently started falling after hitting a peak.

http://www.nzherald.co.nz/business/...=markets&thesecondsubsection=worldsharemarket

The stock market (US) is regaining some optimism as well after the decline in the crude prices. These trends may be short term and may also be dictated by the November Presidential election, see links below.

http://www.nytimes.com/2004/08/21/business/21stox.html

http://usa.mediamonitors.net/content/view/full/9076/

Charmed :)
 
C

Carl Keller

#19
I know the market and design is still in its infancy. however they will need to address the consumer demand for power everything.

Right now a full tilt SUV has AC, power windows, power locks, power seats, power sunroof, CD, DVD player, surround sound amps, On Star, GPS, Headlight power washers/wipers, traction control, electric anti-lock, ....Need I go on?

That takes a LOT more power than a few batteries and a lawnmower engine.

Carl-
 
V

vanputten

#20
An additional metric that we all could use is Pounds of CO2 Created per 1,000 miles. Are we trying to sub-optimize our individual process (needs-experience) or maximize the system in which we operate?

Regards, Dirk
 

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