My 1993 300SD MB manual provides for
adding kerosene (I think up to 50%).
Since you are in CA, I see you reason
to add kerosene. If you want a good
additive, use the Redline products
(check the PartsShop here - good price).
Engine rebuilds are VERY expensive so I
wouldn't use my car to experiment.
I have heard of a lot of tales about what
can be done to a diesel engine. I think
that a lot depends on the year, make and
model of the car. Often times, these
tales are told by someone who has never
owned a diesel.
Personally, I depend on my car running
every day. I am anal about maintenance
and repairs. I only use MB parts, etc.
However, I have 149,000 miles on the car
and people think that it is a new car.
(in fairness though, I had to have the
engine rebuilt due to a head gasket failure
at 102k miles).