the dealership where i change my oil uses quaker state. the toyota dealership where my wife has her "free" oil changes uses quaker state. i recall quite a few years ago q.s. supposedly had a problem with sludge build up or something like that. Do yall know anything about quaker state oils? i sure liked the fact that we didn't have to pay for oil changes on my wifes car but im nervous about the quaker state. i checked the oil website vertrk and shortspark had mentioned but got complete "tired head" and didn't find much about that particular oil. I sure would appreciate legitament input from you folks if you have any.