I live in Argentina and we have a solid Compressed Natural Gas distribution infraestructure. Its a lot cheaper than gasoline and the conversions are relatively cheap especially on old cars.
BUT, it has a lot of issues. You should go electric ( full, not hybrid) and skip methane.
Heres why:
1. Safety: We have had some nice explosions here until very strict safety measures and regulations where in place. You are driving around with a big steel cilinder at high pressure (200 Bar about 2900 psi ) in case of a fire there are safety valves and the tank should not explode, but it surely burns completely everithing near it. Not too different from gasoline now that I think of it. Stations will refuse to refill if you dont have all the certificates for the tank or tanks (they are risking their lives otherwise). This involves hydraulic tests every 5 years and if the tank doesnt pass its destroyed, cant be repaired.
2. Weight: Only steel tanks are allowed. There are nice alumium reinforced with carbon fiber tanks, but these had caused many explosions. The fiber reinforcement breaks easiy with friction from the mounts or in a fire and they were banned many years ago.So, heavy steel tanks and heavy mounts for safety, these are less important in big pickups or trucks, but for small cars implies reinforced suspension.
3. Autonomy: Its increasingly dangerous and technically difficult to use higher pressure than 200 Bar, so the tanks have limited capacity. Tipical ranges are around 120 Km ( 75 miles) for a small engine ( 2 liter or less ) and a big tank.
4. Less power: Methane occupies more volume than vaporized gasoline, so the ideal mix in the engine gives less energy, some say about a 10 % less in my (subjective) experience seemed more than that.
5.Engine stress: One way to offset the power loss is to change the engine computer settings, this can be used to get more HP from an engine running with gasoline, and I used to get more from the engine while running with methane. This increases temperature, leading to early engine failure, its especially hard on the exhaust valves.
Some years ago I had a relatively long commute to work, so I bought a new car ( a Citroen Berlingo, a small van) and get to convert it to what was at the time state of the art in CNG. I had three small tanks for better autonomy ( about 200 km, 124 miles ) had to reinforce suspension, changed the engine settings for more power, and used an additional engine computer to regulate the methane mix ( there were cheaper conversions that use a kind of carburetor ). All this looked like a better deal than the same vehicle with a modern diesel engine, and the fuel was a lot cheaper. A year and half later, after two expensive engine repairs and 90000 km ( 56000 miles) , I had sold the car ( and the engine wasn't in great condition). The cost of the car+conversion+repairs+fuel was almost exactly the cost of the diesel version plus the fuel for that mileage. I had saved nothing economically and the car was heavy, with little autonomy and high maintenance.
I think the best you can do with methane is to use it to generate electricity. Modern combined cycle generators are way more eficient than the internal combustion engines in cars, and this offset the distribution and battery losses.
So please, skip the methane in cars, it's not worth the bother.
