zieg72 209 #1 Posted May 21, 2009 I would like to know if the straight weight is the way to go for my 520H. The book says 30W, 40W or 50W for the summer months based on temps. I know that oil technology has improved with time but I would like to hear from you guys with Onan's. Thanks in advance. Share this post Link to post Share on other sites
Hodge71 663 #2 Posted May 21, 2009 I've been using castrol syntec 10w40 in my 416 hydro. It seems to love it. I know its not a 520 but its basically the same engine thought. Yours is a 20 Hp onan and mine is a 16 hp onan. hope it helps. I was actually thinking of changing the tranny to 10w30 syntec when i change it in the fall. gotta do more research on compatability though. :drool: Share this post Link to post Share on other sites
520H4me 0 #3 Posted May 26, 2009 I am a fan of synthetics, but given the dirty environment that I run my tractor in, I change the oil/filter fairly regularly. I run 30 weight with a lot of Lucas in it as my Onan is kinda tired due to neglect of the prior owner. Share this post Link to post Share on other sites
TLWheelHorse 0 #4 Posted May 27, 2009 I will be using this.. http://www.amsoil.com/StoreFront/ase.aspx I am an amsoil dealer.... so i have no other choice lol. Share this post Link to post Share on other sites
