Just changed oil on my YM30 a few weeks ago. Took about 3.5 quarts and I didn't change the filter (only about 15 hours since previous filter change). As long as you are inbetween the marks on the dip stick you should be OK; however, I would add another 8 oz to get the oil level further up the stick. Be sure to let motor sit for 10-15 minutes to ensure that all of the oil has migrated into the oil pan before adding oil.