NYMEX NY Harbor ULSD futures.
curl "https://metalapi.com/api/v1/latest?api_key=YOUR_API_KEY&base=USD¤cies=HEATINGOIL"
{ "success": true, "base": "USD", "rates": { "HEATINGOIL": 0.2088991017, "USDHEATINGOIL": 4.787 } }