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This blog is expressly directed to readers who do not have strong training or backgrounds in science, with the intent of helping them grasp the underpinnings of this important issue. I'm going to present an ongoing series of posts that will develop various aspects of the science of global warming, its causes and possible methods for minimizing its advance and overcoming at least partially its detrimental effects.

Each post will begin with a capsule summary. It will then proceed with captioned sections to amplify and justify the statements and conclusions of the summary. I'll present images and tables where helpful to develop a point, since "a picture is worth a thousand words".

Wednesday, September 8, 2010

Saving CO2 Emissions At No Cost

Summary:  Using gasoline with higher octane ratings can result in lower CO2 emission from your car.

Reduce carbon emissions.  We all know that burning fossil fuels, such as gasoline, releases the carbon dioxide (CO2) that contributes to global warming into the atmosphere. What would you say if you could effortlessly reduce your carbon footprint while driving, all at no cost to you?  

Use gasoline with higher octane ratings to reduce the gasoline used per mile traveled.  Well, you probably can. You see, when you use higher octane gas in your car, you actually get more miles to each gallon of fuel, because that fuel is more effective in the engine. In fact, I have found, in the two cars I’ve owned recently, that going up to 89 octane gas from 87 (regular) increases the gas mileage consistently by about 5%. So you go about 5% further on a gallon of 89 than on 87. (So far I’ve not tried any higher octane rating than 89.) Now, 89 octane gas generally costs about 5% more than 87 octane.

So if you divide the increased cost of the 89 octane into the increased gas mileage, your cost per mile comes out essentially unchanged!

Cost per mile = (Cost per gallon) / (Miles per gallon)

Reduce the cost per mile.  And it’s really the cost per mile that should govern your gas purchasing decision, not the cost per gallon.  (Please note, however, that both these cars had manual transmissions. Cars with automatic transmissions should behave similarly, but you should verify this. If you need help on how to measure your gas mileage, please see below.)

So by not spending any more money, you can effortlessly decrease the amount of CO2 released in every trip you take by about 5%. That’s certainly worth the effort since it costs you nothing. Since every reduction in atmospheric accumulation of CO2 is significant, this is an easy, cost-free way of making a contribution to slow global warming.

Everyone should start this simple habit right away, and make a difference!


1. The web sites of the American Petroleum Institute ( and Wikipedia ( explain in detail that gasoline blends with different octane ratings were originally designed to avoid premature ignition, or “knocking”, in carburetor-fueled engines. Nowadays, however, practically all cars have computer-controlled fuel injection, and many adjust the timing of the spark that ignites the fuel mixture to prevent knocking, so that knock ratings are less relevant for their original purpose nowadays. Other popular web sites may state that higher octane gasolines do not increase gas mileage. All I can say is that consistently for several years I find the results I outlined above hold true. The best way to find out is to evaluate your own gas mileage.

2. To calculate your gas mileage, follow these simple steps.

a) Once in a gas station, before refilling, or definitely before leaving the station, either set a trip mileage meter in your speedometer module to 0.0, or else make a note of your actual first odometer reading for the starting mileage.

b) Fill your tank until the automatic shutoff of the pump activates.

c) Drive your car, preferably over highways rather than city, until the fuel gauge shows near empty (but don’t run out!).

d) Now enter a gas station to refill and write down the mileage on your trip meter; this gives your actual miles traveled. Otherwise record your second odometer reading for the ending mileage and subtract the ending mileage from the starting mileage to give you your actual miles driven.

e) Refill your tank again to the automatic shutoff of the pump and now make a note of the number of gallons delivered to your tank from the reading on the pump’s meter.

f) Divide the number of miles driven (step d)) by the number of gallons of gas delivered (step e)). The result is your miles per gallon, or gas mileage.

Repeat this process for regular gas (87 octane), and for midgrade (89 octane) or higher (91 or higher). You probably should wait one tankful after filling with the higher grade for the first time to flush out any residual 87 octane left in the tank. Measure the gas mileage for the higher octane gas on the second refilling with the high octane gas.

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