I keep getting a misfire on number 4, spark plug also had oil on it!

 

Welcome to the site..

What vehicle, engine?

 

it's a 2003 Ford ranger edge 3.0L. The owner took really good care of the engine. It sat 5 years, he nvr had it over 45-50mph. I changed the oil and added an additive that replaces a quart of oil, only used half. That's when it started to get worse and oil showed up on the spark plug!