We suffered with this battle for a year with our Mooney's heater cable.
We pulled the cable out, soaked the sheeth in a bucket of goo for weeks
etc. In the end we could never de-goo it enough to make it slide
easily. Since Mooney wanted $500 for a new cable I wasn't going to
replace it. I ended up getting lucky one day and found someone willing
to sell me theirs. We never were able to de-goo the original
cable/sheeth after about a year of actively trying anything we could
think of.

-Robert