Garmin is Misleading the Enviro-Lemmings with Bad Science

So this is the story. My sons bought me a GPS for Father’s day. I did my research and finally picked out a Garmin Nuvi a couple of weeks ago. It is really a pretty cool toy! The Nuvi has an awesome EcoChallenge feature, which tracks mileage, fuel economy, trip efficiency, etc. The user inputs the fuel economy averages for city and highway driving, their fuel cost and the Nuvi calculates the rest. One of the included features is the users Carbon Footprint Estimate. However, according to my calculations their software is flawed resulting in an errant Carbon Footprint Estimate.

I am including my exchange with Garmin Support.

Dear Garmin,
How is the carbon footprint calculated by my Nuvi? I don't think it is at all accurate.

Dear Don,
Thank you for contacting Garmin International. I am happy to assist you.

When you enter your car information and fuel information. It will track how fast you drive and so on and use a its [sic] program to get you a good idea of what your footprint might be. It is only a [sic] idea it will not be 100%. it [sic] is made to help you try to do a few thing different like keep at a good speed and thing [sic] like that.

Please let me know if I can help further.

With Best Regards,
Dustin P.
Product Support Specialist

Dear Garmin,
Thank you, I understand the concept. My question is more correctly this, how does the EcoChallenge software make the calculation? The reason I ask is when dealing with matter, volume, and mass you cannot increase the mass of a substance. (Didn’t we learn this at some point in our middle school science class at the public school?)

For instance in my situation I used 13.8 gallons of gasoline the weight of that amount of fuel is just under 85 lbs. If the gasoline was made up of only carbon molecules, then my maximum carbon emissions could only weigh just under 85 lbs. (We know that fuel has many molecular elements which make up the chemical we know as gasoline, so the carbon mass of the emissions is much smaller.) The volume of the fuel as a liquid will be smaller than the volume of the same fuel as a gas (vapor) having less density, resulting in fewer molecules of carbon per cubic centimeter, however the mass will not have changed. The calculation from my Nuvi suggests my carbon footprint is nearly three times that amount at 249 lbs. Garmin’s EcoChallenge software is flawed providing misleading results. If we want to be serious and clear about the "Global Warming – Climate Change" debate we should ensure that we are using accurate science with valid results. A small deviation of even 10 percent in accuracy would be more tolerable than a 300 percent error.

Dear Don,
Thank you for contacting Garmin International. I will be happy to help you with this.

Unfortunately the information you are requesting is proprietary information. Our engineering team does not release the specifics of how our products work.

If there is anything else I can help you with feel free to email me back.

With Best Regards,
Anthony G.
Product Support Specialist

Dear Garmin,

I still love my Nuvi. I like that it calculates my gas mileage for every tank of gas, but I don’t trust your EcoChallenge Carbon Footprint Estimate. I will say again, “If we want to be serious and clear about the "Global Warming – Climate Change" debate we should ensure that we are using accurate science…” Not just fear mongering.

I am not an Enviro-Lemming.

DL