I bought a new Scag W/B hydro last spring. In the fall I changed the hydro oil and filter and used Castrol 20W50 oil. My question is did my mower come from the factory filled with synthetic hydro oil? None of my literature says anything other than what viscosity to use so I am guessing it's regular oil. What got me wondering was a Husqvarna catalog that I was reading today and it seems their mowers are filled with Mobil1 from the factory. I just want to be sure I did not mix oils by mistake.