Client

How to set/get fuel?

First you need to retrieve the vehicle entity handle (with ox_lib cache.vehicle)

Retrieve Vehicle Entity

    local playerPed = PlayerPedId()
    local vehicle = GetVehiclePedIsIn(playerPed, false)

Then you need to set the statebag for get/set the fuel

Statebag Setup

    -- previous locals to get the vehicle entity
    Entity(vehicle).state.fuel

Now you can get or set the value of the Statebag in this ways

Get Fuel Level

    local playerPed = PlayerPedId()
    local vehicle = GetVehiclePedIsIn(playerPed, false)
    
    local fuel = Entity(vehicle).state.fuel

Set Fuel Level

    local playerPed = PlayerPedId()
    local vehicle = GetVehiclePedIsIn(playerPed, false)
    
    Entity(vehicle).state.fuel = 100

Set Fuel Level (with server replication)

    local playerPed = PlayerPedId()
    local vehicle = GetVehiclePedIsIn(playerPed, false)
    
    Entity(vehicle).state:set("fuel", 100, true)