This paper proposed a sustainable method for fuel recovery from the oil sludge (OS) such as oil field sludge (OFS) and oil tank sludge (OTS) by the ash-catalyzed pyrolysis-reforming processes. The highest oil yield can reach 35.5% from the OTS co-pyrolysis with the OFS-ash. It can be attributed to the presence of iron and sulfur elements in the OFS-ash. Co-pyrolysis with the OFS-ash could also improve the contact between the OS and the catalyst resulting in the increase of oil yield. Compared with the OFS, oil recovery from the OTS was more considerable. However, the OFS-ash possessed a better catalytic performance on the pyrolysis vapor upgrading because of high metal (e.g., iron) contents. In addition, the highest HHV and cetane index (46.1 MJ/kg and 38.51) could be obtained when the oil from OFS co-pyrolysis with the OFS-ash was blended with the diesel with a volume ratio of 1:10. The range of carbon distillation of the mixed fuels (C7-C26) was identical with the diesel oil. And the saturate contents of the mixed fuels increased with the increase of the oil proportion. Therefore, mixing with the OS oil could slightly improve the quality of diesel. (C) 2016 Elsevier Ltd. All rights reserved.