Skydrol LD-4 was introduced in 1977 , and is well known around the world. At the time of its introduction it was a breakthrough product, solving problems of valve erosion and thermal stability common in earlier fluids. Its excellent thermal stability under real world conditions has given it a reputation as the gold standard among Type IV fluids. Skydrol LD-4 features low density, excellent thermal stability, valve erosion prevention, and deposit control.