Hello, in mid 2014 I bought degassing system with large vacuum pump. In last year I was using it very rarely - like once per 2 months, for degassing urethanes and low viscosity silicone. Now I need to degas high viscosity silicone, but pump pull only to 27in. hg. I changed oil two times on fresh but I still can't reach 29 inches. What are the possibilities in that situation?