Abstract: A crude shale oil is produced by in situ retorting of oil shale in a fragmented permeable mass of formation particles containing oil shale in an in situ oil shale retort in a subterranean formation containing oil shale. A combustion zone is advanced through the fragmented mass by introducing an oxygen containing gas to the mass on the trailing side of the combustion zone and withdrawing an off gas from the fragmented mass on the advancing side of the combustion zone. Gas flow advances the combustion zone through the fragmented mass and transfers heat of combustion to a retorting zone on the advancing side of the combustion zone. Kerogen in oil shale in the retorting zone is decomposed to produce gaseous and liquid products including crude shale oil. Crude shale oil produced by such a process and having characteristics described herein is withdrawn from the fragmented mass on the advancing side of the retorting zone.