I was coming out of Wal Mart tonight and there was this older lady starting her minivan. She started it and it had a very loud tick. Much louder than a dry start tick. I went over to her and asked her when the last time she checked her oil was. She said it had been a long time. I noticed the CHECK ENGINE SOON light was on. I told her that her engine sounded like it was low on oil and would she like me to check the level for her. The mileage was just about 100,000. She thanked me and said she would have her husband check it in the morning. My question is can you really tell by ear what the problem is or is it just a guess?