what do you guys use? the factory recommeds 80W-90 i think right? i wanna change mine again with full synthetic but i can only find quaker state 75W-140 full syn at the local parts store. the other synthetics that they have in 80W 90 are store brand names that i dont want. will the quaker state 75W 140 be ok or do i have to go somewhere else and find an 80W-90??