First, I'm curious as to who actually manufactures Honda Pro GN4 10W-40 dino oil? If anyone knows this, please let me know. Also, if anyone has the spec sheet for this oil please let me know. Now, I'm trying to decide if I should keep using Honda Pro GN4 (dino oil) in my 2005 Honda Rancher AT or switch to something else such as Castrol. FYI....it has the same basic transmission as the Honda Rubicon, which is a Hondamatic.....hydro type drive. Previously, in my old 1988 Honda 300 all I ever used was Castrol GTX 10W-40 and I never had any issues with anything engine/transmission related. I'm considering using it in my new Rancher, but some people say that you should only use the special ATV/Motorcycle oil. Does anyone have any advice on this? Thanks for any info!