He must have lousy mechanics ... two of the fleet managers (both small commercial operations) that I know rave about how NG is less wear and tear on their engines and require less maintenance.
I may have spoken too soon about the mechanic’s skills. The trucks in the commercial fleet I’m aware of are after market re-fits of 1-ton pickups. I have heard from others that some fleet vehicles are not conversions but are designed to be CNG vehicles and are relatively “new” engines. As such, some of them do not have a good track record when it comes to maintenance as the engine designs have not been proven by the market.
I was planning to purchase a bi-fuel (diesel / cng) pickup for my next vehicle. I will have to look at this again.