Pat, it all depends on the state of the engine. If it is fairly clean providing you give it a good run first, then drain it straight away, you should be OK. If the engine is dirty and the oil very black, you can buy a Wynn's flushing additive to add to the oil, when it's hot, let it run for a while and then drain off. Which ever method you use, always change the oil filter. If you do want to flush it, the Wynn's treatment is by far the cheapest, as nowadays filling up with flushing oil is very expensive.