Problems selecting 3rd

Shift fork problem im thinking. But we dont want to go there, change to a synthetic oil 20w50 and if your already using that type then do an oil change to see if that wont help it a bit. I've noticed that everytime i change my oil the shifting gets a "little" easier. I used to have problems of mine popping out of second a lot.. when it does that, i change the oil and make firm positive shifts to make sure i dont cause any further damage, and to work/wear the gears together again so the wont slip.After your oil change see if you can skip third and go into fouth then step it back down into third, try this over and over again. Then from a stop try to see if you can normally go into third gear if you cant... well you probably know what that means. let me know if this was helpful thanks.