Lowered 1950, Hydraulic fluid! in Buick - Post War Posted February 16, 2011 So I lowered my 1950 Super and the front road really hard, would slam down just on the smallest bumps. So I checked the Hydraulic fluid in the knee action shocks, there was nothing in them! So try to find the correct fluid..almost impossible.. However I went to harbor freight and found:15 Oz. Hydraulic and Jack OilSo if you're looking for the correct fluid for those old knee action shocks, its cheap and works great!