What kind of oil goes in a 4 cycle string trimmer. Is Castrol 30 weight O.K. or should I use something else?

30wt oil is ok just remember this unit only takes acouple of onces of oil good luck

Sure, of course myself would use synthetic.... but 30 weights fine.... as long as its hd-30.

this particular trimmer uses .6 oz of oil every hour so be sure to check it often bcause a new short block is 72$ plus labor............P.S..dont over-fill either or your breather will suck oil into the carb and it wont run