Just wanted to know if anyone here has used engine oil flush during oil changes? Experiences and opinions? Yay or nay? Can it do damage? If you do use it, which brand? My father serviced his car recently and mentioned he uses engine flush once in a while but I've never done one before and not sure if it should be done? Any issues for cars that have been serviced generally on time and done less than 100,000km for the FJ?