Almost all oils come with a dilution rate. If you have a reference book for essential oils it will often say to dilute the oil 50:50 or maybe 80:20. That means that for every drop of essential oil...
At the top of the filter is a rubber seal. Sometimes when you remove the old filter that rubber seal stays in place and when you screw the new filter on the oil will spew out between the two seals....
Its possible you didn't properly install the oil filter. ie its miss-threaded or not tightened properly or too tight. You may have also left the old gasket from the old filter on. Also if you did not...