Started out as Butane or LPG (50 60 70s) which worked pretty good but lost some power. You had to buy tax stamp and log , account for miles and pay more if you went over stamp mileage.

Then in 70 80 s they switched to propane another LPG (lower btu) power and mileage went way down. Ran hot and burned valves.

Now day they trying to use Compressed Natural Gas (4000PSI) in stainless steel fiberglass wrap tanks. Not enough CNG in bottles to be worth your time and they take up a lot of space.
Some people are giving CNG a try on local short routes but there are not many station around and you don't get many miles on fill up.

Some OTR truckers are using Diesel engines and engine management systems injecting about 50% CNG to engine under load. Their tanks are cryogenic LNG tanks and LNG is converted by vaporizer LNG to CNG for engine use. Sound very dangerous to me to put and 18 wheeler on ISHW with either CNG or LNG because of the nature of high compress gas (4000PSI) or LNG at -273 F.

I'd definitely have a line ran to my patio for a natural gas grill, never having to swap out bottles is a nice feature.

Big Iron outdoor gas feed Fire Pit that would glow red on a cold night..

It's the best not having to worry about that crap and having multiple bottles lying around.