October 23 (SeeNews) - Moody's Investors Service on Thursday downgraded the corporate family rating on Bulgaria's fuel retailer Petrol to Caa1 from B2 and the ratings assigned to the senior unsecured guaranteed 100 million euro ($128.7 million) Eurobond to Caa2/LGD 5 (74%) from B3 / LGD 5 (73%).