dont think there are any other rubber parts to worry about and i was told by an engineer and ford diesel owner that the injector has no internal rubber parts although i dont know for 100% sure. i think the big problem and only one are the fuel lines; which over time will swell from the vegtable oil properties thus leading to eventual degrading and a lot of pieces of rubber floating around. wish i had an older diesel to use my fuel in... won't put it in my 2004, trying to find a 94- ford or dodge or pre 85 mercedes