CNG fuel

Lots of present advertising from proponents of CNG for automobiles. Some questions:

1-what is relative fuel use? $/Mile and expected range with a fill up with CNG?

What is typical tank installed with conversion?

2-What could I expect with Federal and State taxation?

3-Is a converted car able to alternatively use gasoline if necessary?

You might want to visit a CNG specific site. While there are CNG vehicles out there, they’re way too small a niche to have the knowledge common.

Part of the reason why CNG/LPG conversions were once very popular was that the fueling systems used were fairly similar to a carburetor in terms of mounting and operating so it was a very easy conversion and there were dual mode CNG/LPG Carburetor/Regulators out there that would allow you to run on both. For a modern car, however, the fuel systems have become far more complicated and at this point you have to buy a purpose-built CNG car (such as the Honda Civic GX) that will only run on CNG.

Your fuel mileage on a CNG car is going to be somewhat less than the gasoline version (although the mileage hit on the Civic GX is amazingly low, only losing about one or two MPG’s over the gas version).

Now, the tricky part about it is the economics. The price of road CNG varies immensely from place to place. Most places apply the highway tax to it, in which case it will typically be about 40-50 cents cheaper than regular unleaded. Some places either don’t apply it or also subsidize it in which case it can be significantly cheaper-- I’ve seen it some places for as low as 1.60 or so, although most places that don’t tax you at the pump still expect you to fill out some paperwork and pay the tax some other way. If you live somewhere that the CNG is only marginally cheaper than the unleaded, often times the reduced efficiency of the CNG vehicle eats up any savings from the cheaper fuel. With the Civic, you mostly have to ask yourself if it’s worth the inconvenience of not being able to fuel up everywhere-- it definitely wouldn’t be a good road trip car!

CNG is a low-density fuel. Your range between fill-ups will be short. In a conversion, you must find room for the very high pressure storage tanks and you SHOULD consider their safety in the event of an accident. In a FACTORY installation, they will have done that for you…

Simple conversions can not take advantage of the higher knock resistance of the fuel compared to gasoline so they have lower power and the already-mentioned higher weight. Even some factory CNG options have this problem since the manufacturers did not want to make a low number engine run specially for CNG.

You can get home refueling pumps for CNG. Check the web or with your local gas company. There may be state and federal subsidies you can use. The home refueling stations are costly, but if you got out of it, you could always sell it. I would see if you can find a CNG car. Look at eBay for some idea. I think the price of used ones has gone up a lot lately.

Some other things to keep in mind, especially if buying a used CNG car are, the tanks need to be tested periodically, maybe once a decade. Service intervals are a lot longer for propane and natural gas vehicles and the engines last a lot longer because they burn much, much cleaner. CNG vehicles can get you into HOV lanes with only one person in the car in some locations, check your area.

check it out here:

  1. Cost of fuel, here in OK is about 1/3 that of petrol. But, your “tank” will only go about 1/2 as far before you run out.

  2. Included in the price above.

  3. Maybe - but it’s quite expensive - $5K seems to be the low end for a small vehicle, with it going higher for larger ones. Most systems look like they spray into the intake of the intake manifold, instead of replacing the fuel injectors - I assume to allow running on petrol if CNG is not available.

All the engines I’ve seen, except for the VW TSI CNG, are non turbo-charged basic engines that are not as efficient (or powerful) to start with. Hopefully VW, as well as others, bring the TSI CNG vehicles to market here, I think they would sell pretty well along with the Phil device.