What trans oil if you can't find the castrol?
Royal purple Royal Purple Gear Oil
or
amsoil AMSOIL - Synthetic Manual Transmission and Transaxle Gear Lube 75W-90 (MTG) ?

 

Thanks very very much.

 

I use the amsoil, good stuff! and it says right on the bottle meets all specs of the NV4500

 

Cant go wrong with the Amsoil.

 

I use Royal Purple in mine. Mostly because I try to stay away from the "Amsoil is god" crowd. Ams is a good oil and I use it, just not in everything. If you were to need a quart, could you find a place to buy some? Out in the sticks? My $.02.

 

Thats why you buy a little extra to have some on hand.

I used to feel the same way...but after using every kind of oil out there - finally arrived at Amsoil. They are 1 stop shopping. You can get whatever you need and not have to drive across town 3 times to get what you need. JMO. Im defintely not an "Amsoil flag waver" - but its a great product - plain and simple.

 

Rebuilt mine and the guy at Blumenthal said Royal Purple would work fine.. Mine was rebuilt with the new all metal syncros.

 

Thats fine, but you dont have the carbon fibre synchros anymore. This could cost someone a transmission.

The Royal Purple is a GL-5 oil and the NV-4500HD calls for a GL-4 oil - which is Castrol Syntorque or equivalent (Amsoil). The Royal Purple gear oil listed does not look to be equivalent to me.