SR-71 also used fuel as its hydraulic fluid.
It’s true....leaked like a sieve when on the ground. It all sealed up in the air at altitude. I used to watch them while on the flight line at Kadena headed west to parts supposed to be unknown.
Watched them coming back, too. One high altitude loop/descend around the field and landed from very high start point. More like a controlled crash.
The SR-71 is truly extraordinary.
I’m still in awe of the B-52.
Still in service since the 1950’s.
In 1980 I traversed the aircraft from its cockpit to tail. For such a large plane I was amazed by how little space there was in its interior. We had to literally crawl on narrow cat walks from nose to tail.