</font><font color="blue" class="small">( adding 1/2 quart mmo to the oil in place of 1/2 quart of oil )</font>
Chris, I've mentioned before on TBN that in '56, when my Dad owned a Texaco service station, one of our regular customers had us do that all the time. He only wanted Texaco non-detergent oil and a pint of Marvel Mystery Oil at each oil change. I believe it was a 1950 Ford he had; only 6 years old, but very high mileage, and clean as a pin.