Depends on the engine design, and whether it was optimized for the fuel being fed to it, or just a comprimise. E85, and E10 are prime examples of wasting fuel in an engine that was not designed to burn them specifically.
The railroads already utilize LNG and CNG fueled locomotives, and they use
them in the most demanding operations: yard switching, and hump & trim sets. And the fuel savings from those operations, along with reduced maintanence costs, have more than made up for the initial stuctural costs.
Sounds like they are used in places at most a few miles from refueling. All these celebrations of LNG are always trash trucks or something that is a mile or two from refuel, never venturing farther.
You can’t haul food to grocery stores that way, and in the end that is the only thing that matters.
BTW, the tank in question losing liquid to gas just sitting is the tank at the refueling point. I’ve seen estimates that 30% of the energy in nat gas is used up converting it to LNG and wastage per day warming up.