NOVELTY - An isolated organism (A1) for producing a biological oil, comprises an overall index for fatty acid efficiency one (OILE1) of at least 5.1, and is calculated by specific relation.    USE - As isolated organism for producing biological oil or biofuel (claimed); and in compression engines.    ADVANTAGE - The isolated organism has a cell density of at least 115 g/l; has a fatty acid content of at least 49% on a dry mass basis; has a 24 hour peak fatty acid productivity of at least 30 g/l/day; and has yield of fatty acid on oxygen of more than 0.4 g of fatty acids produced per gram of oxygen consumed. The method provides economic conversion of renewable carbon sources to fuels.    DETAILED DESCRIPTION - An isolated organism (A1) for producing a biological oil, comprises an overall index for fatty acid efficiency one (OILE1) of at least 5.1, and is calculated by OILE1=C'x D'x F', where C' is fatly acid productivity in grams per liter per day (g/l/day); D' is fatty acid yield in grams of fatty acids produced per grams of feedstock consumed, and F' is extraction efficiency on % of total fatty acid content basis. INDEPENDENT CLAIMS are included for the following:    (1) biological oil or biofuel comprising or made from fatty acids made from the isolated organism (A1);    (2) producing (M1) biological oil, involving producing organism comprising fatty acids, and removing the fatty acids from the organism to form the biological oil, where the organism meets or exceeds at least two metrics, each metric comprising a cell density of at least 115 g/l, a fatty acid content of at least 49% on a dry mass basis, a fatty acid productivity of at least 15 g/l/day, a fatty acid yield of at least 0.175 g of fatty acids produced per grams of feedstock consumed, a 24 hour peak fatty acid productivity of at least 30 g/l/day, or a yield of fatty acid on oxygen of more than 0.4 g of fatty acids produced per gram of oxygen consumed; and    (3) biological oil or biofuel comprising or made from fatty acids made by the method (M1).