hi guys i think i have a hydraulic tappet thats sticking so i googled tappet cleaner and a chap who said he had been a mechanic for 40+ years said that tappet cleaner was a rip off and the best method was to drain 1/2 ltr of engine oil out then add 1/2ltr of atf and drive for approx 300 miles then carry out an oil and filter change.does this seem right and has anyone ever done this.