Comments

• One Car versus Fleet Flip on 06/23/2008 at 8:50 AM

  Posts: 5 Avg Rating:

  There is nothing wrong with MPG for comparing one car to another.  Clearly driving the 50 MPG car is far better than the 14 MPG vehicle. When you get into a fleet of vehicles (2 or more) then you get counter-intuitive results like the above. All you need to do is tell people that if they are driving more than one vehicle then they need to look at the MPG statistics more carefully. The alternative suggested leads to exactly the same result when comparing one versus a fleet of vehicles. Rate this comment: (Reply)

• 	The Canadian way alerion on 06/23/2008 at 8:58 AM
  Posts: 1 Avg Rating:	The gas consumption of new cars in Canada is rated in liters/100 kilometers. One liter/100 km. is the equivalent of ~.43 US gallons/100 miles. For example the Toyota Prius uses about 5 liters/100 km. or 2.1 gallons to travel 100 miles. Barry G. Rate this comment: (Reply)

• 	catching-up to Europe tplum@plumhall.com on 06/23/2008 at 10:02 AM
  Posts: 1 Avg Rating:	In Europe the standard fuel-efficiency measure is liters-per-hundred-kilometers.  Kevin Bullis's post  makes a persuasive argument for shifting the US measure to miles-per-hundred-gallons. Rate this comment: (Reply)

  • 	Re: catching-up to Europe blunney on 06/23/2008 at 11:01 AM
    Posts: 15 Avg Rating:	Kevin Bullis' post also makes a persuasive argument for passing fifth-grade math. Rate this comment: (Reply)

• Delta or incremental? rhutzul on 06/23/2008 at 10:56 AM

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  Based on the question actually posed - which saves more gas rather than the question answered - which initial choice has the smallest incremental impact it's still best to trade in the "guzzler" than it is the "sipper". It's a contrived scenario design to illustrate a point - albeit poorly - that the greatest impact, (financial, environmental or otherwise) comes from using LESS gas in total, rather than using less gas relative to what you're using today.  In fact, the right answers are then a) ride your bike or, (possibly more practically) b) telecommute whenever you can. Since not everyone's ready to wedge the kids into a fuel sipping hybrid for an 8-hour drive to Grandma's house, we should be encouraging people to select the most fuel efficient method to accomplish their objective...if there's an option to avoid using gas, take it - if you're commuting on your own, use the smaller fuel sipping option - if you've done your absolute best to pack lightly but still need the extra space, use the smallest,(which usually correlated with the most fuel efficient) Crossover/SUV that meets your needs. Realistically, that strategy has a better chance of creating the desired impact of less gas usage overall... Rate this comment: (Reply)

• 	c.n.g. porosity on 06/23/2008 at 11:39 AM
  Posts: 3 Avg Rating:	Litres per 100 kilometres. This is the universal way of determining fuel usage.(Move into the 80,s) go with c.n.g or better yet liquid n.g. Lastly, force your car insurance company to allow you to switch plates according to what is the most efficient vehicle at the time.                               Thanks, Clint Rate this comment: (Reply)

  • 	Re: c.n.g. mkogrady on 06/25/2008 at 7:36 PM
    Posts: 90 Avg Rating:	Actually - just convert your pre-flex fuel vehicle to a flex fuel vehicle for about $500 (unless you live in Californy) and then use a blend of 35% gas to 65% E85 and reduce your costs by taking advantage of the BTU's in the gas and the 50 cents per gallon subsidy of Ethanol to drop your cost per mile from about 19 cents to a little over 16 cents. Rate this comment: (Reply)

    • Economics, not subsidies nekote on 07/08/2008 at 10:47 AM

      Posts: 114 Avg Rating:

      Quite clever, utilizing taxpayer subsidies to drive down the $ per mile cost. Uhhh, are you a taxpayer? After whatever period / amount of initial subsidy, if even truly necessary, quit sticking it to the taxpayer.  Rachet the subsidy (and fuel content mandates) back down to 0. Ethanol *FROM CORN*, has proved to be a horribly uneconomic method of capturing solar energy.  Higher taxes, higher corn / food prices, higher gasoline prices, lower BTU per gallon (thus MPG) of gas(ahol).  Makes no economic sense, at all. Corn now at $7 / bushel, versus fluctuating, for a very long time, between $2 and $3. Rate this comment: (Reply)

• Measuring Efficiency nh on 06/23/2008 at 3:49 PM

  Posts: 3

  In addition to the 'vehicle fleet' example, these calculations can help decide how to spend a fixed amount of money on various efficiency improvements. Often the 'biggest bang for the buck' comes from starting with the most inefficient processes - a small percentage improvement on a large number can make a significant difference. A number of comments have suggested some form of 'gallons/mile' measure. The report Study questions method of listing fuel efficiency supports this idea. At the risk of bringing bad bad memories of 'lowest common demoninators', it is easier to compare two values if the 'per x' value is the same. Miles per gallon is useful in estimating distance given a similar volume of fuel. Gallons per mile is better when trying to estimate the fuel used over a similar amount of distance. In the example above, 12 mpg and 14 mpg are roughly 8.3 g/100miles and 7.1 g/100miles, an improvement of 1.2 g/100miles. In comparison, 34 mpg and 50 mpg are roughly 2.9 g/100miles and 2.0 g/100miles, an improvement of 0.9 g/100miles. It all depends what you are trying to achieve. Rate this comment: (Reply)

  • Re: Measuring Efficiency xxxander1 on 07/22/2008 at 4:59 PM

    Posts: 2

    We should not only measure efficiency, but cost as well (or instead).  What it costs to operate your vehicle varies greatly on your choice of energy.  Terms like MPG & KWH make it difficult to compare Operating Cost or “Efficiency” unless a new term based on “Dollars and Distance” something we ALL understand becomes the standard   “$/100mi.” A “COMMON” standard measurement of “Energy Units per Distance Traveled (EU/DT) could be the base,  and since the "EU" will be comprised of 8 to 12 or more products, the "DT" has to be one standard…..(I say 100 mi.)” so that the “$ cost per Distance Traveled” which is what consumers need to know can always be determined “with grade 5 math” So the near future requires a change in terminology from MPG to EU/DT (EU/100mi) so we can easily determine our “$/100Mi” for the car we own or plan to buy. We now say "my car GETS 25 Miles per gallon.” We should say "my car USES 4 gal. per 100mi.” Assuming $4.00 gas we should say “my car COSTS $16.00 per 100mi. to operate”  or $16/100mi. We might someday soon say “my car USES  ?? KWH per 100mi” and from that the cost is easy to determine. With this change in terminology, no matter what source of energy you choose the comparison will always be "apples to apples" when determining the REAL value/cost of  "$/100mi" I have used KWH as a unit for electrical measurement because I have no idea how “electric units of energy” will be measured, or what those units will be called.  Anyone?????? Rate this comment: (Reply)

    • 	Re: Measuring Efficiency Brian H on 08/21/2008 at 12:05 AM
      Posts: 24 Avg Rating:	The Tesla Roadster comes rated at 33 KWH per 100 miles, so multiply your local electric rate times that to get cost per 100 mi.  Here, it's about 6½¢, so that works out to $2.15/100 mi.  Gasoline here costs about $4.50/USG, so that would be about $18/100 mi for a 25MPG car.  Rate this comment: (Reply)

• A good observation MakeSense on 06/26/2008 at 12:08 PM

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  That's a good suggestion, one that will save energy for many people. For me the take-away is a simple rule of thumb: Upgrade your worst efficiency machines (of any kind) before you upgrade the most efficient. This is also intuitive for most people along the lines of, "I'm happy with my fuel-efficient car; I want to replace my gas guzzler." In fact the best solution to your question would be to replace the 12-mpg car with the 50-mpg car. Most people would do that rather than limit their choices to the two you gave as an illustration. But still, it illustrated a good point. Rate this comment: (Reply)

• 	true energymv on 07/01/2008 at 1:47 PM
  Posts: 18 Avg Rating:	i never thought about it that way, but it's true. MPG is not a very good metric. Gallons per 100 miles or gallons per 10,000 miles would be more useful for the casual car shopper. Uncertainty in the price of oil is an important factor in determining what kind of car people buy these days. Rate this comment: (Reply)

• need $/mi; mi/KWH or mi/BTU nekote on 07/08/2008 at 11:02 AM

  Posts: 114 Avg Rating:

  A "Gallon" continues to become ever less standard / certain - diesel, bio-diesel, vegetable oil, gasoline, gasohol (5%, 10%, 20%, E85, E100), propane, CNG, hydrogen, electrical / battery, ....) An economic measuring stick ($/mile) or energy measuring stick (miles/KWH; miles/BTU) would be better, IMHO, than the widely used MPG (Miles Per Gallon). Maybe the inverses (mi/$, KWH/mi, BTU/mi) would be preferable? Rate this comment: (Reply)

  • Re: need $/mi; mi/KWH or mi/BTU xxxander1 on 07/22/2008 at 3:38 PM

    Posts: 2

    In Canada driving cost is easy to calculate - my Prius uses 4 litres of gas per 100 km at $1.30 per litre that’s $5.20 per 100 km (62 mi.)  My Infinity FX35 uses 18.1 litres per 100 km at $1.40 (premium gas) or $25.34 per 100 km (62 mi)….the cost difference of  $5.20 to $25.43  for the same distance of 100 km (62 mi) is very easy to determine. The U.S, should use “Gal. per 100 mi. (or per 1000 mi.) which makes the REAL value “$ per 100 Mi” easy to figure with "grade 5 math".  Of course it would follow then to use, as needed, “KWH per 100 mi.” as well as “BTU per 100 mi.” or "????", each as easy to convert to the IMPORTANT measure of “$ per 100 mi” (in short: Gallons per 100 mi. not miles per gallon) The only economic question that holds any relevance is after all “$ per 100 mi” (or $ per 1000 mi. or $ per 100 kilometre).  And why is this important, well let’s just take one “alternate fuel” E85, which doesn’t deliver the same power as gas and requires more gal. per 100 mi than gas does, so now try to find the $/100mi cost the old way. However this would require the Government, the Auto Manufacturers and the Schools to agree to a “COMMON” standard measurement of “Energy Units per Distance Traveled (EU/DT) and since the "EU" will be comprised of 8 to 12 or more products, the "DT" has to be one standard…..(I say 100 mi.)” so that the “$ cost per Distance Traveled” which is what consumers need to know can always be determined “with grade 5 math”  So the near future requires a change in terminology from MPG  to  EU/DT (EU/100mi) so we can easily determine our “$/100Mi” for the car we own or plan to buy. We now say "my car GETS 25 Miles per gallon. We should say "my car USES 4 gal. per 100mi. With this change in terminology, no matter what source of energy you choose the comparison will always be "apples to apples" when determining the REAL value 0f "$/100mi" Rate this comment: (Reply)

• 	The correct answer lasertekk on 07/20/2008 at 11:51 AM
  Posts: 18 Avg Rating:	The correct answer is the one that uses the least amount of resources and lessens the overall impact, PERIOD. Rate this comment: (Reply)

• Miles per gallon math davidb@mcbd.com on 07/28/2008 at 12:16 PM

  Posts: 1

  Curious that while Kevins math is correct as far as it goes, no one seems to have considered conferring the 12 and 14 MPG fossil vehicles to the junk yard (where they belong) and replacing either or both with the 34 MPG or 50 MPG options. For my part, I am waiting for the planned but not yet available Zenn Citicar which itself appears to be dependent on the pratical demonstration of a working EEstor supercapacitor battery.  EEstor, where are you? The world is waiting for your invention. Rate this comment: (Reply)