local fuel_values = {
["crude-oil"] = "0.4MJ",
["light-oil"] = "0.9MJ",
["heavy-oil"] = "0.45MJ",
["petroleum-gas"] = "0.45MJ",
["diesel-fuel"] = "1.1MJ",
}
data.raw.item["solid-fuel"].fuel_value = "10MJ"
note that flammable oils seems to overwrite them because it's loaded first