Tire Pressure

Did you know that most drivers lose from 10% to 50% of their car's tire tread life due to poorly maintained air pressure?  Tire disposal is a significant environmental problem.   Another environmental issue is reduced fuel efficiency resulting from the extra energy required for vehicles to travel with under-inflated tires.

You should check tire pressure at least once per month, more often during the summer months when the temperature is hotter.   Always use an accurate air gauge, not those provided at service stations.  They tend to be grossly inaccurate.  Also do not judge air pressure by looking at the tires.

The proper method of checking the air pressure is when the tires are cold.  It is good practice to check first thing in the morning before driving anywhere.  If any of the tires are under-inflated then drive straight to the service station.

If you have to drive your vehicle more than 1 km then the tires are considered "hot". Take another tire pressure measurement with your accurate gauge and note the difference from cold temperature.  Inflate the tire(s) to a level equal to the manufacturer recommended cold temperature plus the difference at high temperature.

Make sure that the tires are equipped with valve caps to keep out moisture.   Moisture will cause air to leak from the tire faster. 

Manual versus Automatic Transmission

Should you buy a car with manual transmission or automatic?  If you are going to buy an older car then a manual transmission is more fuel efficient than an automatic by 5% - 15%.  This is only true if driven in a fuel-efficient manner.  One should always shift gears at lower RPMs.  Shifting early will reduce acceleration but increase fuel efficiency. 
In newer cars with five or six speed automatic transmissions there is no clear advantage of manual over automatic.  And in fact you may get 5 mpg better with an automatic on some car models such as the Toyota RAV4, and the FJ Cruiser.

MPGe

MPGe:  The New Measure of Efficiency

by Steve Auger

GM's recent claim of 230 MPG for the Chevy Volt has raised eyebrows and sent engineers and analysts scrambling to figure out the truth behind the claim.  In actuality, the claim of 230 MPG is only accurate provided the Chevy Volt is driven 51.1 miles.  If the calculation had been based on 200 miles then the MPG would be substantially less.  And the gallons of gasoline are not particularly meaningful in any case since the vehicle is primarily electricity powered.

MPG is D E A D

Yes, that is correct.  And it has been the case for some time.  But the question remains as to what measure will take it's place.  The clearest alternative that I have seen is defined at the Progressive Automotive XPrize website.  After all, they are in the business of measuring/judging fuel efficiency.   The term they use is MPGe (Miles Per Gallon Energy Equivalent).   The formula is:

MPGe =  (miles driven) / [(total energy of all fuels consumed)/(energy of one gallon of gasoline)])

They provide an easy-to-use spreadsheet for converting different fuel types (including electricity) to MPGe.  (Go to  Progressive Automotive XPrize and follow link to the spreadsheet.)

Now the real question is whether or not this is a fair measure?  It seems to me that what is really important is the well-to-wheel calculation, not tank-to-wheel.  Well-to-wheel puts a whole new slant on the business of green automobile technology and will ultimately eliminate such technologies as hydrogen fuel cells.

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