Lots of miles but wonder if the CNG helps. Gasoline has some blowby and does contaminate the oil, haven't thought about it but if CNG doesn't contaminate the oil as much maybe better oil life and lubrication. If its had regular repair and maintenance should be pretty good but Id expect to have to fix some things. Keep us posted on how it performs. Lots of knowledgable folks here.
If I think mine is slow I go out and ride my Honda Metropolitan scooter. After that everything is fast!