Joe, Try REDLINE (co.) diesel additive.
Either one of the 2 products as they are
likely the same.
The 1 oz. oil is safe also.

__________________
1979 300D 220 K miles
1995 C280 109 K miles
1992 Cadillac Eldorado Touring Coupe 57K miles SOLD
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1979 240D 140Kmiles (bought for parents) *SOLD.
SAN FRANCISCO/(*San Diego)
1989 300SE 148 K miles *SOLD