Who makes Honda Pro GN4?

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Mar 26, 2004
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!
I have this same machine and I use the Mobil MX4 10W40. If you use this oil you will notice a huge improvement in the transmission operation and the reduced noise levels over the Honda oil. The synthetic appears to make a better hydrolic drive oil. Also the fan seems to run less?

Now for the motorcycle thing. It is my opinion that you don't have to worry about the friction modifiers because this transmission does not use a wet clutch, but becasue of the 10w40 recommendation the MX4 was my best best choice pick for a synthetic.

I also have a 400EX I'm experimenting with different oils Rotella 5W40 synthetic, Castroil MC 10W40, Mobil MX4 etc.. So far I'm happiest with the Mobil MX4 in the sport bike. The shifting is much smoother.

I run 5 honda ATV's on Amsoil MCV 20W-50, stuff is really the dope, not only can you feel the difference you can hear it..cost about $25.00 for a fill, try it and let me know how you like it.
last year my buddy John was a parts manager at a big cycle shop and he said all Hondaline oils were made by mobil (xom).

please realize that honda sets the specs and that the lowest bidder wins the contract to fill the bottles. so it changes over time.
WOuld you use German Castrol in a honda rancher AT? I am trying to figure out if GC has a lot of moly in it, Because with that model you need to use an oil that does not have a lot of friction modidfiers.

My debate is that moly would not cause any problems in the AT model because the transmission does not have a wet clutch. It is a hydraulic drive.

The only thing I don't know is how the switchable 4x4 works. Does anyone know if a clutch is used to engauge the drive to the front wheels? If it is engauged with splines/gears then I still say moly would be fine.

Brent, you do have a wet clutch in your machine, and its not moly that will cause issues with it. Oil's labeled "energy conserving" on the back of the bottle are the oils to run away from.

Also, the Rubicon has a one of a kind Hydrostatic/Hydromechanical type tranny that also surprisingly has a wet clutch too! Your Rancher does not have a similar tranny to the Ruby, not even close. However, the wet clutches between the two, are similar.

And just to add useless info, all Honda ATV's actually have wet clutches, just not all the same type. They are all technically vulnerable to "energy conserving" oils. Some people get lucky, but it is a risk.

Stay safe and use oils specifically labeled for ATV or Motorcycles, and pick a weight based on your owners manual. Its really that simple.

Selectable 4x4 Honda's are engaged via magnetic clutch. Using moly grease on the shaft splines has nothing to do with engangement of clutches. Magnetic, or not. Grease on the shaft will never effect 4x4 engagement.
Awe, dang it. I think I mess'ed up Honda models. The Rancher does have a simialr tranny to the Rubicon. Sorry about that.

All other statements remain.
Ok I thought moly was a friction modifier. Can someone tell me what friction modifiers are? My manual specifically states not to use oil with Friction Modifiers. With that said, would it be safe to use German Castrol in my Honda Rancher AT?
i raced with GC and had it tested. it performed VERY well!!!
meaning it lasted an entire enduro and didn't shear out of grade.
a good winter oil, but not something i will use on a regular basis.
why? too expensive and my manual says 30wt isn't enough for my texas summers. would probably be just fine in ohio.
The purpose of the friction modifier is to REDUCE, not increase friction.

Wet clutchs need friction to function.

Automotive oils generally are not good for ATV's unless they meet JASO MA/MA2, if this is not on the label, don't use it in you Honda ATV

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