Yes you can. I have been using Walmart branded 20-50 in my Gt2542 ever since I first changed it around 150 hours. It is now over 1000 hours and hydro seems as good as new. I don't know if information is still there but when I decided to change my fluid even though operators manual didn't say to, I found info on Hydro Gear site that said to use 20-50 conventional or syn. I have changed mine with conventional around every 100 hours.