I have a PA-28 140 with the 160hp upgrade. I don't have any fancy engine instruments to help me lean it propertly. All I have is the tach, airspeed indicator and oil temp gage. My question is how do you lean the engine to save the most fuel with doing any damage to the thing. My normal procedure is to get to cruise alt. and speed then reduce rpm to cruise and lean the engine til I get a drop in rpm and enrich alittle. But I'm afarid I'm doing damage to the engine by doing this. I have no way to see how hot it is running other than oil temps. Thanks.