I have a Craftsman 19.5 hp lawn tractor that was new in 2000. There is a sticker under the hood on the right side that says it takes 48 ounces of oil, the owner's manual says 3 pints.
There are factors that will effect this answer. What model the tractor is, what engine it has, what transmission, what condition, where it is being sold, what time of year it is being sold etc......