Are You Really Driving On The Cheap?

Honda Civic GX trunk

Reduced trunk of the Honda Civic GX. Anyone for beans on toast with a glass of milk?

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.


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.


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.

Rickety signature.
Owners of NGVs please comment on your experiences.


  1. driving school runcorn says

    Helpful info. Fortunate me I discovered your site by chance, and I am stunned why this accident did not happened earlier!
    I bookmarked it.

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