I put a quart of Marvel Mystery Oil in there with an oil change, and run it
half as long as I would a regular oil change. Old timers used to use a
quart of diesel. It works to free up hydraulic lifters, and since we have
few hot rodders, most 99.999999999999999999% of the population has
hydraulics, not solid lifters. I DO NOT do this if I am going to drive
that distance at highway speeds, but rather if I am going to do a mix of
freeway speeds and round town driving. Drain, and change oil. I also like
to use a probe that fits through the drain hole and sprays a high pressure
jet onto the screen that is over the oil pick up in the pan. This dislodges
crud that accumulates on the screen and inside the pan that normally does
not drain out in a regular oil change. First time, put a filter under the
outflow, and spend a full 15 minutes, or until you stop getting crap out,
which will be 30 minutes if you really have a long extension and work it.
Extends the life of motors tremendously. If you have a parts washer, this
will do, but the higher the pressure, the more crud you will kick loose. A
magnet in the drain plug also picks up ferrous metal fragments, and the new
supermagnets epoxied onto the drain plug catches anything ferrous that is
floating in the oil.
Advice from an old fart hotrodder who cut his teeth on '56 Chevies and 300
imho, jmho, ymmv, etc, etc, etc
Run it like you stole it.