Back in the day my dad was a head mechanic he would run 3 quarts kerosene with 2 quarts oil through the engine he got lots of my frinds and I to do it to never had an issue BUT and this is a BIG BUT ( almost as big as my ex girfriends) these were cars from the 50's, 60's and 70's we were driving then. Don't know how it would affect the newer type of seal materials, gaskets, pcm etc