An engine is provided which includes an oil gallery, a base attaching seat in an engine frame wall, and a base for component mounting attached to the base attaching seat. An oil cooler and an oil filter are mounted on the base for component mounting, and the base attaching seat is provided with an oil inlet communicating with an upstream-side passage of the oil gallery, and an oil outlet communicating with a downstream-side passage of the oil gallery. Attaching the base for component mounting to the base attaching seat allows engine oil flowing into the oil inlet of the base attaching seat from the upstream-side passage of the oil gallery to pass the base for component mounting, the oil cooler, and the oil filter, and flow out of the oil outlet of the base attaching seat to the downstream-side passage of the oil gallery.
