Hello, I had my car parked for about a week or two in front of my neighbors house who does like me very much (no other place on the street to park) the car was turned on and driven every few days. Today when I started driving the car it was making a loud knocking sound, I pulled out the dip stick and the oil was sludge, last oil change I got was about 8k miles ago. Is it possible my neighbor did something to my car to turn the oil into sludge?