Okay so I know that many of you don't have access to CNG. A friend of mine has a 2007 Chevrolet 2500 HD with Duramax Diesel and just installed a new CNG conversion tank etc. He says he is now getting 55mpg diesel and using 2 gallons of CNG. CNG here is $0.75/gallon and diesel is $3.55/gallon. The conversion claims a 100 hp gain at the wheel. Before the conversion he was getting 17mpg which would be a cost of $0.208/mile at current prices. and after the conversion its $0.092/mile. His truck is lifted 6" and on 35" tires. If the numbers are real then a normal truck or diesel car would get even better mileage and cost savings. My wifes car gets 30 mpg gasoline and with this conversion it'd be cheaper to drive the big diesel truck. The conversion kit was $3500 installed but he knew somebody who knew somebody so he helped with the conversion and it only cost $2800 for him. Still saving $0.11/mile would add up quick and pay for itself in $30,000 miles. Of course if the price of diesel went down then it wouldn't pay off as quickly but I don't see that happening. Anybody had any experience with CNG? I'm curious and may be looking at trading off my gas guzzler for a diesel to put the conversion kit on.