If it was as easy to fuel and to find propane as gas...you will use way more propane than gas..
I drove a government pickup that used propane and gasoline...less power ..less fuel mileage...plus after so many propane fuel fills we were told to run a tank of gasoline through it..this was in early 2000's...plus in cold weather the truck did not want to start as easily on propane.
In the shop a lot for propane problems...they would catch us running on gas...rather than fooling with the propane....
they were 4.6 v8 fords back then...
seems like the Compressed natural gas engines gave less problems but you did not have a gas tank..so if you ran out of natural gas you had to call a tow truck...also much more complicated (high pressure) than propane.
my personal experience...