Thats the prob with PVC hose , most of the stuff on general sale is not oil resistant regardless of what might be claimed on packaging. Silicone also , unless it is the oil resistant type it will eventually be a problem. There is an oil resistant type of PVC hose available , but trying to identify it is almost impossible. Go for the Tygon brand , expensive but the best. When buying rubber hose go for a well known brand like Gates or Dayco , this will avoid getting rubbish imported junk. Alternatively , use the everyday PVC hose and replace it at least every annually.