well my friend has a 2001 ford f150 with 97k miles. hes parents bought it brand new and took very good care of it, than they gave it to him when he turned 18. he has given the best care u can and maintenance. full synthetic oil changed every 4k miles, fuel filter changed, antifreeze, everything.he called me yesterday and told me the truck was hesitating and got a CEL light. so i scan and got po 305. misfire in piston #5. i thought it was a bad coil, or fuel injector. so i take out the coil and the plug also. to my amazement the plug came out FULL of oil. in the tip and the threads. theres no leaking gaskets, and i took out other spark plugs and theyre clean as hell. the only thing i think it can be is a broken piston ring and or a worn valve guide :dunno: . he has money for the worst case scenario but it wasnt in his plans to get a new engine. i told him what i think it could be , but could there be something else????? idk, what else can i check??? or could be???? rigth after i cleaned and put the spark plug back in it worked fine and didnt hesitate . but if its burning oil it wont take long to start hesitating again.