Here is some advice I'm re-quoting from blaise_f, who really knows his way around leather:
Originally Posted by
blaise_f
"Oil" is a broad term. Use NOTHING petroleum based - that attacks, dries and destroys leather. Proper restoration requires patience of a saint. Soak in neatsfoot oil (NOT compound), let it soak in, naturally "dry", repeat and massage cracks with spoon.
(Quote from
this thread.)
For what it's worth, I had a fair amount of success reviving (not quite restoring) a well-worn Ideale saddle. There are still some cracks, mostly on the sides, which I did not try addressing using the advice above. However, after soaking in a bucket of water for a couple hours, then reshaping, and adding some proofhide, the saddle has remained hard and I'm optimistic I will get many more miles of usage.
Before:
After:
