Are you really driving on the cheap? That’s the question an owner of a NGV may be asked occasionally. The only monetary disavantage of a NGV is the initial cost which can be alleviated by buying used. In my prior post I listed CNG advantages, many of which are monetary, which is the focus of this article.

As the owner of a Honda Civic GX, for the last two and a half months I have collected data to see how much I am saving and how much you could save.

The CNG savings I have split into two groups, fuel savings and vehicle savings.

Fuel Savings

For a period of 2 1/2 months from 23 November 2009 to 5 February 2010 I noted several metrics. At each refueling I recorded miles driven, gallons used, price per gallon of CNG, and the cost of regular gasoline. I also calculated averages over this time period.

I drove 2,381 miles, needing 18 fill ups, 5 of which were only partial. By this I mean that a NGV is dependent on how well the fuel is compressed. Lower PSI means less fuel in the tank. It isn’t a big deal, it just means you get to drive less before the next fill up.

I refueled on average every 4.1 days, having averaged 132 miles. The most I drove between refueling was 184 miles, the least 91 miles. The range was reduced by the partial fill ups. New 3,600 PSI pumps are being installed which will add 15% more fuel to the tank. My average MPG was 31 which was all city driving.

The cost per gallon was 93 cents, which includes 8 1/2 cents Alternative Fuels Tax, except for one fill up at the University of Utah which was $1/gallon. A Division of Fleet Operations & Surplus Services Gascard is required at the U of U, Utah State, and Jordan, Alpine, and Granite School Districts. The average fill up was 4.32 gallons costing $4.03 (not a typo).

The most I filled my tank was with 5.688 gallons. The rated capacity is 7.2 gallons at 3,000 psi and 8 gallons at 3,600 psi. In theory one could drive 240 miles on a full tank. Don’t ask me what you do if you run out of gas, I don’t like to think about that.

In summary, I spent $72.62 on CNG to drive 2,381 miles while regular gas would have cost $220.89. Regular gas varied from a low of $2.49 to $2.71 a gallon, the average being $2.57. My savings was $128.27, the difference between CNG and gasoline.

Vehicle Savings

There are vehicle savings because of my switch from a 2007 Honda Accord V6, rated at 18 mpg in city driving. By driving the Civic GX the savings amounted to $141.20 over the same time period. This is the difference in the cost of gasoline the V6 would have required.

EMPG

A coworker and I use Equivalent Miles Per Gallon (EMPG) as a fun measure of the value CNG delivers. EMPG is the mpg you would get if the extra cost of gasoline was converted to mpg using a NGV thus:

Cost of gasoline / Cost of CNG x CNG mpg = Equivalent mpg

Using our formula I came up with an average of 86 EMPG. This will easily exceed over 100 EMPG this summer.

Summary

The total savings is $269.47 over 2,381 miles or 11.3 cents a mile. Or put another way: it cost 3 cents a mile. The savings will increase this summer when gasoline rises. CNG prices will likely be fixed at 93 cents even when gasoline crosses $4 a gallon. At least for a time.

The biggest downside is the reduced range and sparse filling stations. A minor inconvenience is the reduced trunk as shown in the photograph. But these are not monetary disadvantages, it just means a few more minutes to stop and refuel.

If you live in Utah it is well worth it for 93 cents gas.

Owners of NGVs please comment on your experiences.