My mechanic friend said his Dad always swore by STP Oil treatment. Knowing what's in it, I would suggest it only for a 70's car that is EXPECTING ZDDP in the oil. Alternately, there are other oil treatments that are said to suppliment in the same fashion, like Justice Bros, Motor Honey, etc. Having experimented with JB's Oil tretment.. after getting a flame war started on this board, I have actually found it to have some cleaning properties to it.. along with a "ZDDP Substitute"... Their Customer service is secretive about it. Again, OK for hotter than [censored] summers, or vintage motors.. I don't choose to use it at ALL in winter or in young motors.

If you have an 30 year old engine that burns a little oil, the product will be more at home in that engine than it will in a younger engine.