Friday, 21 May 2010

Three Laws of Car Fuel Economy

Okay, the price of car fuel is going through the roof. What are we going to do about it? Drive less?--That's a very good way to stop global warming. Not a good way to be at Aunt Martha's picnic this weekend.

We could get a super-efficient car (like mine--gets 65 mpg) or get a super-efficient engine (like the one under development--see the full theory at, but you would probably miss the picnic. How about some ways to really cut the cost of gasoline TODAY?

That brings me to a new set of rules. You might say they are Rogers' Laws of Car Fuel Economy. These were mostly known before. They may not actually work for everybody's car, depending on how the car was engineered. A well-engineered car should follow the rules to a "T."

Here are the rules. By following them, you should be able to cut your fuel costs by 20% or more, starting today!

Three Laws of Car Fuel Economy
Ernest Rogers May, 2008

1. In highway driving, for each 5 mph that you slow down, your mileage will increase by 10%.

2. For any trip with a present average speed of (mph) and fuel consumption of (mpg), if you speed up to save time, the extra fuel you will use can be estimated by—

Extra gallons = (mph /mpg) x (minutes saved /35)

In words, if you divide your normal speed by your usual mpg, then multiply by minutes you want to save (by speeding up) and divide by 35, that’s the amount of extra fuel you can expect to use. It is a handy rule to see the fuel cost for speeding to save time.

3. Very efficient drivers use pedals less and can get 30% better mileage than inefficient drivers.

Thursday, 20 May 2010

Facts on global warming

Global warming has so many implications for industries and government, besides being an environmental issue, that there are powerful forces on all sides trying to convince us of one reality or another. You can only know the truth by digging it up for yourself. Here are some helps in that direction.

1. I just finished reading "The discovery of Global Warming" by Spencer Weart. (Harvard Univ. Press, 2003) This is an account of the history of the subject, written from an expert viewpoint, but fairly balanced. Weart is the director of the Center for History of Physics at the American Institute of Physics--great credentials. This is a great book, but won't tell you details of the science, just how various evidence has fit together over time. It's quite an eye-opener. Only a year old, it is already out of date on technical grounds. You can probably check out this book in a college library, I did.

2. A big sticking point among some "professionals" has been the publications of John Christy (U. of Alabama, Huntsville) which have shown no warming trends in satellite measurements of atmospheric temperature. His measurements have been a great comfort to the present Republican administration, which abandoned the Kyoto agreements that the U.S. had helped to forge. Christy's work is now being seriously challenged by two recent publications that show large warming trends based on satellite data. (If interested, I think you can get a recent Christy paper on-line: John R. Christy et al. "Update on Microwave-based Atmospheric Temperatures from UAH" 15th Symposium on Global Change and Climate Variations. 2003) Christy has a web site: Following are the challenging references.

3. Qiang Fu et el., "Contribution of Stratospheric Cooling to Satellite-inferred Tropospheric Temperature Trends" Nature 429, 55-58 (6 May 2004). Fu says that Christy overlooked the influence of tropospheric cooling in his calculations. He makes the correction, and finds a large warming trend. This appears to be a hot topic right now. Hard copies of this issue may not have reached library shelves yet, but a helpful librarian can download the paper for you.

4. Menglin Jin, "Analysis of Land Skin Temperature Using AVHRR Observations" Bul. of the American Meteorological Soc. (BAMS) April, 2004, p. 587-600. Jin analyzes satellite data to obtain earth surface temperature. He also shows a large warming trend. This is a major paper, lots of references. Most of the figures are in color, good luck getting it copied.

Final word: It can be shown logically that a warming earth does not necessary cause the upper troposphere to get warmer, as Christy would argue. I will provide this in a future post.

Ernie Rogers

Mad about fuel cost Save 10% right now

Are you mad about the present cost of fuel? You can save about 10% or more on fuel cost right now, and help to stop global warming at the same time.

I am working on ways to reduce fuel consumption in transportation, such as reducing aerodynamic drag. So, I experiment with my car-- I measure my fuel economy all the time. Here are some facts about highway driving:

* Reducing highway speed from 70 mph to 65 mph saves about 8% of fuel.

* Reducting speed from 75 mph to 70 mph saves about 10% on fuel.

* At 80 mph, you are throwing fuel away. If you drive over 80 mph and push the pedal any time you feel the need, then you have the potential to save as much as 30% of fuel usage.

Hey, if you are seriously angry about the price of fuel, you can bring it down, if you can just relax a little when you drive. Give it a try. Let me know your results.

Good luck