I just tried the latest version of this plugin on my test server and everything seems to be working correctly.
I spawned a modular car with 0 consumption and only 1 low grade fuel, and the fuel settings persisted after a server restart.
{
"Vehicles": {
"4module_car_spawned.entity": {
"StartingFuel": 1,
"LockFuelContainer": false,
"FuelPerSecond": null,
"IdleFuelPerSecond": null,
"MaxFuelPerSecond": null
},
"3module_car_spawned.entity": {
"StartingFuel": 1,
"LockFuelContainer": false,
"FuelPerSecond": null,
"IdleFuelPerSecond": null,
"MaxFuelPerSecond": null
},
"2module_car_spawned.entity": {
"StartingFuel": 1,
"LockFuelContainer": false,
"FuelPerSecond": null,
"IdleFuelPerSecond": null,
"MaxFuelPerSecond": null
}
},
"ModularCarsSpawnFullHealth": false,
"EngineModules": {
"1module_cockpit_with_engine": {
"PartsTier": 3,
"LockContainer": false,
"IdleFuelPerSecond": 0.0,
"MaxFuelPerSecond": 0.0
},
"1module_engine": {
"PartsTier": 3,
"LockContainer": false,
"IdleFuelPerSecond": 0.0,
"MaxFuelPerSecond": 0.0
}
}
}