I guess the only way to tell if its regular oil is to have it tested. I can't remember the lab that tests it (I believe its called black something or another) but they should be able to tell you. I'd just switch it over to synthetic right away, this way, YOU know what's in there. I just did my first oil change and incase you don't know, it takes 8.5 quarts of oil and the oil filter is special to our cars. I got (2) oil filters from the dealership for a little over $25.00. I bought two just to have an extra one for next time. I prefer Mobil 1, but there's many synthetics out there, good luck!