mac here, regarding oil on coil packs , as an electrician , the basic facts are that oil ,virtually all ,even motor oil (except for that now defunct Arco graphite -conducts electricity) is a total insulator . For your highest power [email protected]
utilities ,like 75KV, 150KV (kilo-volts) etc. will have oil inside the switches and x-formers as insulator and coolant ! So if motor oil is sprayed on a coilpack virtually nothing no ,shorting will "immediately" happen or I'm betting even a submerged in oil coilpack won't "definitely nor immediately" have to to fail . for all automotive elecronics must to a high degree be resistant / immune to motor oil & greases which permeate all engines soon in time !
Here's the kicker - IN TIME though use of poor plastics ,and shoddy parts designs ,oil will cause slow -progressive failure , though much slower in better designed & quality components .I've learned myself that checking the plugs is so often the best , first thing to look at ,they virtually "tell all" and can point to coil pack ,oil consumption ,detonation , cracked porcelin , ad infinitum .