You may be able to find an online manual. Otherwise, if you'll only use it during hot summer months, then 30w is okay. However, if you are going to use it in the cooler months of spring and fall as well, then maybe you should use 10w30. I use 30w in my two older engines. I have a newer John Deere and I use 10w30 in it. I may use a little more oil, but since I check it everytime I mow, keeping it full is no issue.