If your 1980 300SD injection pump has the original rubber seals in it, I expect that with time, you car will be capable of making a sizeable mark when parked for a week.

Here's what Coda did before I re-sealed the injection pump during a 9 day trip:
Coda, 1986 300SDL, the journey continues........

__________________
daw_two
Germantown, TN

Links:
Sold last car --- 05/2012 1984 300D Light Ivory, Red interior
Cluster Needles Paint
New Old Stock (NOS) parts

Past:
3/2008 1986 300SDL "Coda"
04/2010 1965 190D(c) "Ben"
& many more