NOVELTY - A upgrading (M1) bio-oil involves: combining bio-oil comprising oxygenated hydrocarbons and having total oxygen content greater than 5 wt.% with diluent thus forming feed stream; charging the feed stream to preheater and heating feed stream to 20-450 degrees C thus forming heated feed stream; charging heated feed stream to hydrodeoxygenation unit at 300-500 degrees C; and separating at least a portion of the partially upgraded bio-oil from the effluent stream thus forming a product stream of partially upgraded bio-oil having total oxygen content lower than the total oxygen content of the bio-oil.    USE - For upgrading bio-oil (claimed); for separating a light fraction, bio-distillate fraction, and heavy fraction from a bio-oil, and for producing renewable distillate including at least in part the bio-distillate fraction and a stabilizing additive.    ADVANTAGE - The method reduces fouling in upgrading equipment, such as a hydrodeoxygenation unit.    DETAILED DESCRIPTION - A upgrading (M1) bio-oil involves: combining a bio-oil comprising oxygenated hydrocarbons and having a total oxygen content greater than 5 wt.% with a diluent thus forming a feed stream; charging the feed stream to a preheater and heating the feed stream to a temperature of 20-450 degrees C in the preheater thus forming a heated feed stream; charging the heated feed stream to a hydrodeoxygenation unit operated at 300-500 degrees C, where at least a portion of the oxygen is removed from the oxygenated hydrocarbons of the bio-oil thus forming an effluent stream comprising the diluent, water, and at least partially upgraded bio-oil; and separating at least a portion of the partially upgraded bio-oil from the effluent stream thus forming a product stream comprising the partially upgraded bio-oil having a total oxygen content lower than the total oxygen content of the bio-oil. INDEPENDENT CLAIMS are included for the following:    (1) upgrading (M2) bio-oil involving: combining a bio-oil comprising oxygenated hydrocarbons and having a total oxygen content greater than about 5 wt.% with a diluent comprising a recycle stream thus forming a feed stream; charging the feed stream to a preheater and heating the feed stream to a temperature of 20-450 degrees C in the preheater thus forming a heated feed stream; charging the heated feed stream to a hydrodeoxygenation unit comprising at least two stages and operated at 300-500 degrees C, where at least a portion of the oxygen is removed from the oxygenated hydrocarbons of the bio-oil thus forming at least one inter-stage stream comprising partially hydrodeoxygenated bio-oil and an effluent stream comprising the diluent, water, and an at least partially upgraded bio-oil; separating at least a portion of the at least partially upgraded bio-oil from the effluent stream thus forming a product stream comprising the at least partially upgraded bio-oil having a total oxygen content lower than the total oxygen content of the bio-oil, where at least one inter-stage stream and the product stream are each at a higher temperature than the bio-oil; and utilizing as the recycle stream a portion of at least one of: the inter-stage stream, and the product stream;    (2) upgrading (M3) bio-oil involving: combining a bio-oil comprising oxygenated hydrocarbons and having a total oxygen content greater than about 5 wt.% with a diluent thus forming a first feed stream; charging the first feed stream to a preheater and heating the first feed stream to 20-100 degrees C in the preheater thus forming a heated first feed stream; combining a recycle stream having a temperature of 100-460 degrees C with the heated first feed stream thereby forming a second feed stream having a temperature of 20-450 degrees C; charging the second feed stream to a hydrodeoxygenation unit comprising at least two stages and operated at a temperature of 300-500 degrees C, where at least a portion of the oxygen is removed from the oxygenated hydrocarbons of the bio-oil thus forming at least one inter-stage stream comprising partially hydrodeoxygenated bio-oil and an effluent stream comprising the diluent, water, and at least partially upgraded bio-oil; separating at least a portion of the partially upgraded bio-oil from the effluent stream thus forming a product stream comprising the at least partially upgraded bio-oil having a total oxygen content lower than the total oxygen content of the bio-oil, where the inter-stage stream and the product stream are each at a higher temperature than the bio-oil; and utilizing as the recycle stream a portion of at least one of: the inter-stage stream, and the product stream; and    (3) upgrading (M4) bio-oil involving: combining a bio-oil comprising oxygenated hydrocarbons and having a total oxygen content greater than 5 wt.% with a diluent thus forming a feed stream; charging a portion of the feed stream as a preheater feed stream to a preheater and heating the preheater feed stream to a temperature of 20-450 degrees C in the preheater thus forming a heated feed stream; charging the heated feed stream to a hydrodeoxygenation unit comprising at least two stages and operated at 300-500 degrees C, where at least a portion of the oxygen is removed from the oxygenated hydrocarbons of the bio-oil thus forming at least one inter-stage stream comprising partially hydrodeoxygenated bio-oil and an effluent stream comprising the diluent, water, and an at least partially upgraded bio-oil; charging a portion of the feed stream as a quench to at least one of the inter-stage streams to thus form a quenched inter-stage stream and control the temperature of the downstream stages; and separating at least a portion of the at least partially upgraded bio-oil from the effluent stream thus forming a product stream comprising the at least partially upgraded bio-oil having a total oxygen content lower than the total oxygen content of the bio-oil.