I put about 6-8 oz in my tank (83 300D). An earlier post apparently figured out the exact mixing ratio.

In my N14 Red Top, I put 1 qt per 142 gal tank. does better than half-gallon of Lucas per tank.

and my fuel mileage difference is 2 mpg, on average on the Benz.

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1983 300D, the "Avocado"
1976 240D, 4-spd the "Pumpkin", SOLD to Pierre
1984 190D, 2.2L, 5-spd, my intro to MBZ diesels, crashed into in 2002