The first and most obvious answer to this would always be please refer to your manufacturers instruction manual, as you will almost always find the answer there.
If that fails, a brief visit to the manufacturers web site will probably answer your question equally efficiently.
You can find contact details, including web addresses, for all our brand manufacturers on this website. Just click here.
However, as a general rule, when it comes to 4-stroke oil, MowDirect recommends clean, fresh and newly opened. SAE 30.