Which type of oil and what is the fuel mixture ratio for my Homelite ST-275 UT-20594-2?

At the time of manufacture there existed both 32:1 and 50:1 oils, but the latter is generally recognized as the proper mixture with a quality two stroke oil made for that ratio. Always best to use a name brand oil from a manufacturer of two cycle equipment.

Oh, the parts breakdown is the link below.